WEBVTT 00:00:00.000 --> 00:00:02.700 Okay, let's unpack this. We are opening up the 00:00:02.700 --> 00:00:06.379 story of the man whose name is synonymous with 00:00:06.379 --> 00:00:10.099 the very blueprint of life, Gregor Mendel. He 00:00:10.099 --> 00:00:12.560 was a quiet, perpetually struggling Austrian 00:00:12.560 --> 00:00:15.740 friar who, using nothing more than, you know, 00:00:15.779 --> 00:00:17.739 pea plants and some pretty rigorous mathematics, 00:00:18.160 --> 00:00:21.519 unlocked the fundamental laws of heredity. We're 00:00:21.519 --> 00:00:23.039 talking about the father of modern genetics. 00:00:23.260 --> 00:00:26.239 It's a title he absolutely earned, but the story 00:00:26.239 --> 00:00:28.559 of how he earned it and how long it took for 00:00:28.559 --> 00:00:31.359 the world to notice is just incredible. It's 00:00:31.359 --> 00:00:33.719 an incredible story of delayed recognition for 00:00:33.719 --> 00:00:37.960 sure. So between 1856 and 1863, Mendel conducts 00:00:37.960 --> 00:00:39.840 the experiments that establish the fundamental 00:00:39.840 --> 00:00:42.979 rules of heredity. Right. And our mission today 00:00:42.979 --> 00:00:45.340 is to really get into how he did that, and maybe 00:00:45.340 --> 00:00:47.340 more importantly, why the scientific community 00:00:47.340 --> 00:00:51.509 just... ignored him for 35 years. 35 years. I 00:00:51.509 --> 00:00:53.869 mean, that's a profound intellectual lag in biology. 00:00:54.109 --> 00:00:55.789 The whole field was basically waiting for his 00:00:55.789 --> 00:00:58.549 discovery. It was. But the real hook here, the 00:00:58.549 --> 00:01:01.429 thing that still gets debated today, is the paradox 00:01:01.429 --> 00:01:04.129 baked right into his data. Yeah, this is the 00:01:04.129 --> 00:01:07.510 really juicy part. Before anyone even had a concept 00:01:07.510 --> 00:01:10.810 of DNA, Mendel just posits the existence of these 00:01:10.810 --> 00:01:13.849 invisible factors, what we now call genes, and 00:01:13.849 --> 00:01:17.170 uses them to predict traits with, well, Stunning 00:01:17.170 --> 00:01:19.489 accuracy. And that's the tension. That's the 00:01:19.489 --> 00:01:22.510 core of it. How could a humble monk working without 00:01:22.510 --> 00:01:25.269 any modern equipment produce results that were 00:01:25.269 --> 00:01:28.489 so mathematically perfect that when a top tier 00:01:28.489 --> 00:01:31.469 statistician analyzed them in the 1930s. A giant 00:01:31.469 --> 00:01:34.150 of the field. A giant. Yes. Ronald Fisher. He 00:01:34.150 --> 00:01:36.689 looked at the data and flagged it as being, and 00:01:36.689 --> 00:01:39.129 this is the quote, implausibly and consistently 00:01:39.129 --> 00:01:42.430 too close to the expected ratios. So too perfect 00:01:42.430 --> 00:01:45.200 to be true. Exactly. It's the Mendelian paradox, 00:01:45.519 --> 00:01:47.400 and it's the mystery at the core of this deep 00:01:47.400 --> 00:01:50.000 dive. We have to decide, or at least explore. 00:01:50.920 --> 00:01:53.260 Was he the luckiest scientist who ever lived 00:01:53.260 --> 00:01:56.060 or did he maybe feel compelled to massage the 00:01:56.060 --> 00:01:58.040 numbers a little to make sure his revolutionary 00:01:58.040 --> 00:02:00.760 theory was heard? To really appreciate the scale 00:02:00.760 --> 00:02:02.920 of Mendel's achievement, I think we have to start 00:02:02.920 --> 00:02:05.579 with his origins. This wasn't a man born into 00:02:05.579 --> 00:02:07.780 the aristocratic scientific elite of Europe. 00:02:08.020 --> 00:02:10.800 Not at all. He was born Johann Mendel in 1822 00:02:10.800 --> 00:02:15.419 in Heinzendorf by Odrau, which was then the Salesian 00:02:15.419 --> 00:02:17.539 part of the Austrian Empire. And his background 00:02:17.539 --> 00:02:20.819 was profoundly humble, agrarian. Absolutely. 00:02:21.000 --> 00:02:23.400 He came from a German -speaking farming family, 00:02:23.460 --> 00:02:25.800 and that farm had been in their family for at 00:02:25.800 --> 00:02:28.800 least 130 years. His early life was just characterized 00:02:28.800 --> 00:02:31.180 by working the soil. He was an active gardener, 00:02:31.180 --> 00:02:34.319 and he studied beekeeping really early on. That 00:02:34.319 --> 00:02:36.520 practical, hands -on connection to agriculture 00:02:36.520 --> 00:02:39.780 is so key, I think, to his later success. He 00:02:39.780 --> 00:02:42.439 wasn't just an abstract thinker. But the path 00:02:42.439 --> 00:02:44.919 from that farm to a university, I mean, it was 00:02:44.919 --> 00:02:47.699 agonizingly difficult. And it really all came 00:02:47.699 --> 00:02:50.120 down to money. He struggled constantly. Through 00:02:50.120 --> 00:02:52.400 his studies at the gymnasium in Trappau and later 00:02:52.400 --> 00:02:54.219 at the Philosophical Institute of the University 00:02:54.219 --> 00:02:57.479 of Alamook, it was a constant battle. The sources 00:02:57.479 --> 00:02:59.879 really show the financial strain was crippling. 00:02:59.960 --> 00:03:02.240 It wasn't just a challenge. It was an existential 00:03:02.240 --> 00:03:05.240 threat to his education. He was constantly plagued 00:03:05.240 --> 00:03:07.680 by illness, partly from overwork and stress, 00:03:07.900 --> 00:03:10.120 and it forced him to take time off multiple times. 00:03:10.560 --> 00:03:12.659 When you read accounts of his early years, the 00:03:12.659 --> 00:03:15.520 anxiety is just relentless. And education was 00:03:15.520 --> 00:03:18.060 this luxury that he perpetually risked losing. 00:03:18.340 --> 00:03:21.599 And the family sacrifice involved is just staggering. 00:03:21.759 --> 00:03:24.039 It wasn't just his own effort. Right. His younger 00:03:24.039 --> 00:03:26.500 sister, Teresa, this part of the story always 00:03:26.500 --> 00:03:29.020 gets me. She was so committed to his education 00:03:29.020 --> 00:03:31.879 that she actually gave him her dowry so he could 00:03:31.879 --> 00:03:35.020 continue his studies. Think about that. That's 00:03:35.020 --> 00:03:37.879 not just support. That is an active foundational 00:03:37.879 --> 00:03:40.740 investment in his future. Yeah. It shows how 00:03:40.740 --> 00:03:42.919 much faith his family had in him. Absolutely. 00:03:43.180 --> 00:03:46.379 And this level of, well, desperation and family 00:03:46.379 --> 00:03:48.960 support is the critical context for his next 00:03:48.960 --> 00:03:51.520 move. Which was becoming a monk. He took the 00:03:51.520 --> 00:03:53.740 name Gregor when he entered the Augustinian St. 00:03:53.840 --> 00:03:56.340 Thomas's Abbey in Brno. And he did this partly 00:03:56.340 --> 00:03:59.020 because the monastery offered intellectual sanctuary 00:03:59.020 --> 00:04:02.539 and... crucially a way to get an education without 00:04:02.539 --> 00:04:05.319 the financial burden. So it wasn't a purely spiritual 00:04:05.319 --> 00:04:07.699 calling, at least not at first. It was a profound 00:04:07.699 --> 00:04:10.219 escape from what he himself described as the 00:04:10.219 --> 00:04:12.560 perpetual anxiety about a means of livelihood. 00:04:12.919 --> 00:04:15.639 The monastery provided stability. It gave him 00:04:15.639 --> 00:04:18.199 the intellectual freedom that a struggling farmer's 00:04:18.199 --> 00:04:20.660 son otherwise could never have afforded. That 00:04:20.660 --> 00:04:22.279 detail just makes him so much more relatable. 00:04:22.579 --> 00:04:25.079 It does. And you have to understand, the Augustinian 00:04:25.079 --> 00:04:28.800 order in Brno was far from being some quiet purely 00:04:28.800 --> 00:04:32.060 spiritual retreat. It was known as a center of 00:04:32.060 --> 00:04:34.959 intellectual life and scientific inquiry. Really? 00:04:35.279 --> 00:04:38.180 Oh, yeah. They valued teaching, research, and 00:04:38.180 --> 00:04:41.680 engagement with the natural sciences. The abbot 00:04:41.680 --> 00:04:44.699 at the time, Cyril Knapp, was a huge proponent 00:04:44.699 --> 00:04:47.259 of scientific investigation. It was the perfect 00:04:47.259 --> 00:04:50.079 place for a mathematically inclined, nature -loving 00:04:50.079 --> 00:04:53.019 individual like Mendel to land. So he gets there, 00:04:53.079 --> 00:04:54.600 but he doesn't just walk into a lab and start 00:04:54.600 --> 00:04:57.250 planting peas. No. Not at all. He was assigned 00:04:57.250 --> 00:04:59.889 as a substitute high school teacher. And interestingly, 00:05:00.189 --> 00:05:02.810 his primary focus after returning from his studies 00:05:02.810 --> 00:05:05.449 at the University of Vienna was physics. And 00:05:05.449 --> 00:05:07.589 he studied under the famous Christian Doppler. 00:05:07.689 --> 00:05:10.089 Yes, the Doppler of the Doppler effect. This 00:05:10.089 --> 00:05:11.949 is a crucial point that so often gets missed 00:05:11.949 --> 00:05:14.629 in the biology textbooks. Mendel's expertise 00:05:14.629 --> 00:05:17.370 was primarily quantitative and observational. 00:05:17.470 --> 00:05:20.370 It was rooted in physics and meteorology, not 00:05:20.370 --> 00:05:23.160 pure botany. So he viewed the natural world as 00:05:23.160 --> 00:05:26.819 a system of measurable, quantifiable laws. Exactly. 00:05:26.939 --> 00:05:29.279 And that explains why his approach to the pea 00:05:29.279 --> 00:05:31.500 plants was so mathematical, so different from 00:05:31.500 --> 00:05:34.060 the descriptive, qualitative botany that was 00:05:34.060 --> 00:05:36.199 common at the time. But here's where the personal 00:05:36.199 --> 00:05:38.920 struggle continues. And I find this detail strangely 00:05:38.920 --> 00:05:41.319 comforting for anyone who's ever felt like an 00:05:41.319 --> 00:05:45.410 imposter. The exam. The exam. Despite the genius 00:05:45.410 --> 00:05:48.189 he would later display, Mendel failed the oral 00:05:48.189 --> 00:05:50.009 portion of the certified high school teacher 00:05:50.009 --> 00:05:53.769 exam. Not once. Not once, but twice. In 1850 00:05:53.769 --> 00:05:56.810 and again in 1856. Can you imagine? You're an 00:05:56.810 --> 00:05:59.509 innovator so far ahead of your time that you 00:05:59.509 --> 00:06:02.009 literally fail the standardized test for the 00:06:02.009 --> 00:06:04.470 job you are about to redefine. It just speaks 00:06:04.470 --> 00:06:07.509 volumes about the disconnect between formal assessment 00:06:07.509 --> 00:06:10.170 and true intellectual breakthrough. The system 00:06:10.170 --> 00:06:11.990 couldn't measure what he was capable of doing. 00:06:12.170 --> 00:06:14.379 But he had mentors. People who saw past those 00:06:14.379 --> 00:06:17.019 exam results. We know his physics teacher, Friedrich 00:06:17.019 --> 00:06:19.560 Franz, was key in recommending him to the Abbey 00:06:19.560 --> 00:06:21.199 in the first place. And then there was Johann 00:06:21.199 --> 00:06:24.139 Karl Nessler. Right. Nessler headed natural history 00:06:24.139 --> 00:06:26.800 at Almach and had already been conducting his 00:06:26.800 --> 00:06:29.100 own research on hereditary traits in sheep and 00:06:29.100 --> 00:06:31.759 plants. This wasn't happening in a complete vacuum. 00:06:32.269 --> 00:06:34.610 So there was an existing, if kind of primitive, 00:06:34.750 --> 00:06:38.189 tradition of studying heredity within the Abbey's 00:06:38.189 --> 00:06:40.490 intellectual sphere. Definitely. And people like 00:06:40.490 --> 00:06:43.110 Alexander Zawadzki also encouraged his research 00:06:43.110 --> 00:06:46.370 in Brano, possibly helping him refine his experimental 00:06:46.370 --> 00:06:49.089 design. He was building on something. So he has 00:06:49.089 --> 00:06:52.540 the mathematical rigor from physics. the agricultural 00:06:52.540 --> 00:06:54.860 background from his childhood, and the support 00:06:54.860 --> 00:06:57.459 of the abbey's intellectual environment. That 00:06:57.459 --> 00:06:59.879 all sets the stage perfectly for his seven years 00:06:59.879 --> 00:07:02.620 in the garden. But that scientific career, as 00:07:02.620 --> 00:07:04.699 we know, was ultimately temporary. It had an 00:07:04.699 --> 00:07:07.959 expiration date. Unfortunately so. In 1867, he 00:07:07.959 --> 00:07:10.540 succeeded the long -serving abbot Cyril Frontichet 00:07:10.540 --> 00:07:13.040 Knapp, and after officially becoming abbot in 00:07:13.040 --> 00:07:16.459 1868, his scientific work largely just ground 00:07:16.459 --> 00:07:18.459 to a halt. The administrative duties completely 00:07:18.459 --> 00:07:20.800 swallowed his time. It's a classic story. He 00:07:20.800 --> 00:07:23.360 traded his trowel and his observation notes for 00:07:23.360 --> 00:07:26.040 accounting ledgers and legal briefs. He became 00:07:26.040 --> 00:07:28.680 immediately and heavily burdened with these duties, 00:07:28.819 --> 00:07:32.040 especially one serious, all -consuming dispute 00:07:32.040 --> 00:07:34.139 with the civil government. The tax dispute. The 00:07:34.139 --> 00:07:37.199 tax dispute, yeah. Overimposing special taxes 00:07:37.199 --> 00:07:39.939 on religious institutions. And that fight consumed 00:07:39.939 --> 00:07:42.860 the last decade and a half of his life. He felt 00:07:42.860 --> 00:07:45.160 it was his duty to protect the Abbeys' intellectual 00:07:45.160 --> 00:07:47.860 and financial independence from what he saw as 00:07:47.860 --> 00:07:50.319 excessive state interference. It was a noble 00:07:50.319 --> 00:07:52.819 cause, for sure, but it meant the world lost 00:07:52.819 --> 00:07:55.220 access to one of its greatest scientific minds 00:07:55.220 --> 00:07:58.680 prematurely. He died in 1884 from chronic nephritis, 00:07:58.920 --> 00:08:01.660 a life cut short by stress and, you know, maybe 00:08:01.660 --> 00:08:03.959 the sheer weight of his responsibilities as Abbot. 00:08:04.379 --> 00:08:06.480 Okay, let's turn now to the work that defines 00:08:06.480 --> 00:08:10.240 him. Those seven years between 1856 and 1863. 00:08:10.699 --> 00:08:13.519 This period, spent in the monastery's substantial 00:08:13.519 --> 00:08:15.959 two -hectare garden. That's nearly five acres. 00:08:16.040 --> 00:08:18.399 It's a serious plot of land. This period yielded 00:08:18.399 --> 00:08:21.339 the very foundation of modern biology. And Mendel's 00:08:21.339 --> 00:08:24.540 success hinged on two things. His choice of organism 00:08:24.540 --> 00:08:27.560 and his methodology. He chose the garden pea, 00:08:27.699 --> 00:08:30.829 pisum sativum. Why peas? What was so special 00:08:30.829 --> 00:08:33.049 about them? Well, the pea plant is scientifically 00:08:33.049 --> 00:08:36.250 ideal for a few reasons. Yeah. First, it naturally 00:08:36.250 --> 00:08:38.710 self -colonates, which means you can easily get 00:08:38.710 --> 00:08:41.309 pure, true breeding lines. But you could also 00:08:41.309 --> 00:08:43.909 easily cross -pollinate them manually, which 00:08:43.909 --> 00:08:45.929 gives you complete control over the experiments. 00:08:46.169 --> 00:08:48.450 You can play God, basically. You decide who the 00:08:48.450 --> 00:08:51.120 parents are. Exactly. And the scale of his work, 00:08:51.200 --> 00:08:53.500 again, it just speaks to his dedication. This 00:08:53.500 --> 00:08:56.259 was painstaking work over seven years, during 00:08:56.259 --> 00:08:58.539 which he cultivated and tested approximately 00:08:58.539 --> 00:09:02.399 28 ,000 plants. 28 ,000? That's not a backyard 00:09:02.399 --> 00:09:04.840 garden project. This was a mass data collection 00:09:04.840 --> 00:09:08.000 effort executed with systematic, almost industrial 00:09:08.000 --> 00:09:10.659 precision. And he was focused on specific, discrete 00:09:10.659 --> 00:09:13.169 differences. He selected seven characteristics 00:09:13.169 --> 00:09:15.710 or traits that appeared to be inherited independently 00:09:15.710 --> 00:09:18.470 of one another. So things like seed shape, was 00:09:18.470 --> 00:09:21.250 it round or was it wrinkled, flower color, purple 00:09:21.250 --> 00:09:24.309 or white, pod shape, plant height. Right. And 00:09:24.309 --> 00:09:26.990 that selection was pure genius. Unlike other 00:09:26.990 --> 00:09:28.889 researchers who got bogged down trying to track 00:09:28.889 --> 00:09:31.610 complex blending traits like, say, the overall 00:09:31.610 --> 00:09:34.269 size of a leaf, Mendel chose traits that were 00:09:34.269 --> 00:09:36.919 clearly binary. They were either or. You're either 00:09:36.919 --> 00:09:39.080 tall or short. Your seeds were either yellow 00:09:39.080 --> 00:09:41.840 or green. There was no in between. And that binary 00:09:41.840 --> 00:09:44.519 choice is what made the underlying mathematical 00:09:44.519 --> 00:09:47.720 patterns just light off the data sheet. His initial 00:09:47.720 --> 00:09:51.080 focus was actually on seed shape. Was it angular 00:09:51.080 --> 00:09:53.820 or was it round? Right. So let's walk everyone 00:09:53.820 --> 00:09:55.799 through the core mechanism because this is where 00:09:55.799 --> 00:09:58.600 his revolutionary insight really lies. He started 00:09:58.600 --> 00:10:01.240 with what he called true breeding plants. And 00:10:01.240 --> 00:10:03.519 that just means that if a plant had yellow seeds 00:10:03.519 --> 00:10:07.200 and you let it self -pollinate, all of its offspring 00:10:07.200 --> 00:10:09.500 would also have yellow seeds, generation after 00:10:09.500 --> 00:10:12.509 generation, a pure line. So he takes a true breeding 00:10:12.509 --> 00:10:14.830 plant for yellow seeds and he crosses it with 00:10:14.830 --> 00:10:17.309 a true breeding plant for green seeds. This is 00:10:17.309 --> 00:10:20.850 the parental or pea generation cross. What happens 00:10:20.850 --> 00:10:24.490 in the resulting first filial or F1 generation? 00:10:24.549 --> 00:10:27.509 This is the first shocker. Every single plant 00:10:27.509 --> 00:10:29.570 in that F1 generation produced yellow seeds. 00:10:29.769 --> 00:10:32.809 The green trait vanished. Completely. Which flew 00:10:32.809 --> 00:10:34.789 in the face of the prevailing theory. Totally. 00:10:35.269 --> 00:10:38.070 If blending inheritance was correct, you should 00:10:38.070 --> 00:10:40.590 have gotten a pale yellow or a light green seed, 00:10:40.789 --> 00:10:43.070 some kind of average of the two parents. But 00:10:43.070 --> 00:10:45.549 no, you got 100 % yellow. This single observation 00:10:45.549 --> 00:10:48.289 is what led him to define the concepts of dominant 00:10:48.289 --> 00:10:51.330 and recessive. Exactly. The yellow trait that 00:10:51.330 --> 00:10:53.289 appeared in the F1 generation, he called that 00:10:53.289 --> 00:10:55.830 dominant. And the green trait that disappeared, 00:10:56.029 --> 00:10:58.429 he called that recessive. This was the proof 00:10:58.429 --> 00:11:01.049 that traits weren't blending. They were discrete 00:11:01.049 --> 00:11:03.419 packets of information. The green information 00:11:03.419 --> 00:11:06.320 was still there somewhere, just masked. That 00:11:06.320 --> 00:11:09.820 masking is the revolutionary concept. So he hypothesized 00:11:09.820 --> 00:11:12.220 that each plant carried two factors for each 00:11:12.220 --> 00:11:14.399 trait, one from each parent. So when he crossed 00:11:14.399 --> 00:11:16.220 a yellow -yellow plant, let's call it big Y, 00:11:16.299 --> 00:11:19.740 big Y, with a green, green plant, little y, little 00:11:19.740 --> 00:11:23.279 y. Every F1 offspring inherited one big Y and 00:11:23.279 --> 00:11:25.379 one little y, making them all big Y, little y 00:11:25.379 --> 00:11:28.419 hybrids. Correct. And since yellow, the big Y, 00:11:28.460 --> 00:11:31.169 is dominant, they all look yellow. The phenotype 00:11:31.169 --> 00:11:33.070 is yellow, even though their genetic makeup, 00:11:33.190 --> 00:11:35.950 their genotype, is hybrid. But the true predictive 00:11:35.950 --> 00:11:39.549 power, the real evidence for his laws, came in 00:11:39.549 --> 00:11:42.710 the next step. He allowed those F1 hybrid plants 00:11:42.710 --> 00:11:45.789 to self -fertilize, producing the F2 generation. 00:11:46.289 --> 00:11:48.090 And this is where the math had to be perfect. 00:11:48.330 --> 00:11:50.690 This is where the pattern reveals itself. Because 00:11:50.690 --> 00:11:54.590 when those big Y little y plants reproduce, they 00:11:54.590 --> 00:11:57.289 separate their factors. That's the law of segregation. 00:11:58.110 --> 00:12:00.789 Each reproductive cell, or gamete, carries either 00:12:00.789 --> 00:12:02.970 the big Y factor or the little y factor, but 00:12:02.970 --> 00:12:05.909 never both. It's essentially a 50 -50 coin flip 00:12:05.909 --> 00:12:08.389 to decide which factor gets passed on. So if 00:12:08.389 --> 00:12:11.029 we visualize it like shuffling two separate factors, 00:12:11.190 --> 00:12:14.250 big Y and little y, from both the male and female 00:12:14.250 --> 00:12:16.330 parts of the flower and then recombining them 00:12:16.330 --> 00:12:18.669 randomly. You get four possible outcomes. You 00:12:18.669 --> 00:12:20.830 can get big Y, big Y. You can get big Y, little 00:12:20.830 --> 00:12:22.990 y. You can get little y, big y. Or you can get 00:12:22.990 --> 00:12:25.029 little y, little y. And because big Y, little 00:12:25.029 --> 00:12:27.110 y, and little y, big y are functionally the same, 00:12:27.149 --> 00:12:29.149 they're both hybrids. And because yellow is dominant, 00:12:29.309 --> 00:12:31.610 you end up with three possible ways to be yellow. 00:12:31.669 --> 00:12:34.409 The purebred and the two hybrids. And only one 00:12:34.409 --> 00:12:37.059 way to be green, the purebred recessive. Which 00:12:37.059 --> 00:12:39.500 is how the recessive green trait reappeared in 00:12:39.500 --> 00:12:41.879 the F2 generation. And it reappeared predictably 00:12:41.879 --> 00:12:45.480 at that famous 3 to 1 phenotypic ratio. For every 00:12:45.480 --> 00:12:48.279 one green pea, he counted roughly three yellow 00:12:48.279 --> 00:12:50.940 peas. The 3 to 1 is what you see. But what you 00:12:50.940 --> 00:12:53.320 don't see, the true invisible structure he unveiled, 00:12:53.559 --> 00:12:56.539 is the underlying 1 to 2 to 1 genotypic ratio. 00:12:56.759 --> 00:12:59.899 That's it. One purebred dominant, two hybrids, 00:12:59.899 --> 00:13:02.500 and one purebred recessive. That was the conceptual 00:13:02.500 --> 00:13:05.580 leap. He was quantifying the invisible. And that's 00:13:05.580 --> 00:13:07.659 not even the whole picture, is it? He then showed 00:13:07.659 --> 00:13:09.759 the law of independent assortment. Which is maybe 00:13:09.759 --> 00:13:12.259 even more profound. It means that the inheritance 00:13:12.259 --> 00:13:15.480 of one trait, say seed color, has absolutely 00:13:15.480 --> 00:13:17.659 no influence on the inheritance of another trait, 00:13:17.720 --> 00:13:20.700 like plant height. So a plant sorting out whether 00:13:20.700 --> 00:13:22.840 it's going to be tall or short and whether its 00:13:22.840 --> 00:13:25.059 seeds are yellow or green, those two decisions 00:13:25.059 --> 00:13:27.159 are made completely separately. Like shuffling 00:13:27.159 --> 00:13:29.659 two entirely different decks of cards. They don't 00:13:29.659 --> 00:13:32.049 affect each other. And this led to even more 00:13:32.049 --> 00:13:34.570 complex but still mathematically precise ratios 00:13:34.570 --> 00:13:37.450 when he looked at two traits at the same time, 00:13:37.470 --> 00:13:40.830 like the famous 9 to 3 to 3 to 1 ratio. His approach 00:13:40.830 --> 00:13:43.909 was just unprecedented. He didn't just describe 00:13:43.909 --> 00:13:46.970 variation. He provided a mechanism and a predictive 00:13:46.970 --> 00:13:49.190 model for it. So he presented this monumental 00:13:49.190 --> 00:13:52.679 work, Versucia, Uber, Flanson, Hybriden. Experiments 00:13:52.679 --> 00:13:54.799 on Plant Hybridization at the Natural History 00:13:54.799 --> 00:13:58.100 Society of Brno in 1865. And it was published 00:13:58.100 --> 00:14:01.080 in their proceedings in 1866. It was effectively 00:14:01.080 --> 00:14:03.899 the rule book for how life passed information 00:14:03.899 --> 00:14:07.299 across generations. And yet what happened next 00:14:07.299 --> 00:14:09.919 is one of the most agonizing footnotes in the 00:14:09.919 --> 00:14:13.179 entire history of science. The publication of 00:14:13.179 --> 00:14:15.720 the rule book led not to a revolution, but to 00:14:15.720 --> 00:14:18.960 a vast deafening silence. We call this period 00:14:18.960 --> 00:14:24.250 from 1865 to 1900. The 35 -year sleep. It's just 00:14:24.250 --> 00:14:26.549 crushing to think about. The paper generated, 00:14:26.669 --> 00:14:28.809 you know, a few favorable reports in local newspapers. 00:14:29.049 --> 00:14:31.070 But that was it. That was the extent of its initial 00:14:31.070 --> 00:14:33.169 impact. It was largely ignored by the international 00:14:33.169 --> 00:14:35.090 scientific community. How many times was it cited? 00:14:35.409 --> 00:14:37.490 About three times over the next three and a half 00:14:37.490 --> 00:14:40.190 decades. That's unbelievable. So why? Why did 00:14:40.190 --> 00:14:42.230 the world look away from such a fundamental discovery? 00:14:42.730 --> 00:14:44.750 Well, part of the problem was how it was framed 00:14:44.750 --> 00:14:47.149 or how it was perceived. It was seen as a paper 00:14:47.149 --> 00:14:49.279 about hybridization. which was a common topic 00:14:49.279 --> 00:14:51.120 for botanists rather than what it actually was, 00:14:51.240 --> 00:14:53.879 a radical quantitative theory of inheritance. 00:14:54.240 --> 00:14:56.419 It was too mathematical for the botanists. And 00:14:56.419 --> 00:14:58.919 too biological for the physicists and mathematicians. 00:14:58.960 --> 00:15:02.259 It fell right into a disciplinary crack. We see 00:15:02.259 --> 00:15:04.460 this today as a painful example of the system 00:15:04.460 --> 00:15:07.679 failing to recognize an obscure, highly original 00:15:07.679 --> 00:15:10.200 innovator, especially one who was working outside 00:15:10.200 --> 00:15:12.039 the established academic centers like Berlin 00:15:12.039 --> 00:15:15.029 or London or Paris. And the historical consequences 00:15:15.029 --> 00:15:18.110 of this oversight are just hard to overstate. 00:15:18.269 --> 00:15:21.149 We know for a fact that Charles Darwin, who was 00:15:21.149 --> 00:15:23.429 desperately trying to figure out how variation 00:15:23.429 --> 00:15:26.470 was inherited to support his theory of natural 00:15:26.470 --> 00:15:29.110 selection. He was completely unaware of Mendel's 00:15:29.110 --> 00:15:31.009 work. There's a story that he had a copy of the 00:15:31.009 --> 00:15:33.509 journal with Mendel's paper in it, but the pages 00:15:33.509 --> 00:15:36.590 were uncut. You never read it. If Darwin had 00:15:36.590 --> 00:15:39.600 held that paper in his hand. If he'd had that 00:15:39.600 --> 00:15:42.460 missing piece of the puzzle that explained particulate 00:15:42.460 --> 00:15:44.940 inheritance instead of blending, I mean, the 00:15:44.940 --> 00:15:47.220 development of genetics and evolutionary biology 00:15:47.220 --> 00:15:49.659 would have accelerated by decades. Oh, absolutely. 00:15:49.940 --> 00:15:52.200 The lack of that connection is one of the great 00:15:52.200 --> 00:15:55.000 historical tragedies of science. It's a huge 00:15:55.000 --> 00:15:57.799 what if. And despite this global cold shoulder, 00:15:58.200 --> 00:16:00.639 Mendel seemed to maintain this astonishing level 00:16:00.639 --> 00:16:03.399 of internal conviction. He even corresponded 00:16:03.399 --> 00:16:05.559 with Carl Nagelli, who was one of the most respected 00:16:05.559 --> 00:16:07.960 botanists of the era. But Neville, who was. was 00:16:07.960 --> 00:16:11.200 a key scientific gatekeeper at the time, he just 00:16:11.200 --> 00:16:14.159 didn't get it. He remained skeptical. He completely 00:16:14.159 --> 00:16:16.559 failed to appreciate the importance of Mendel's 00:16:16.559 --> 00:16:18.779 discoveries. He was stuck in the old paradigm. 00:16:19.000 --> 00:16:21.139 He was stuck in the blending paradigm. He actually 00:16:21.139 --> 00:16:23.700 told Mendel to drop the peas and try his experiments 00:16:23.700 --> 00:16:26.259 on hawkweed instead, which was a terrible suggestion. 00:16:26.700 --> 00:16:29.179 But through all the rejection and skepticism, 00:16:29.460 --> 00:16:32.200 Mendel reportedly told his friend, Gustav von 00:16:32.200 --> 00:16:35.340 Niesel, that now famous line, my time will come. 00:16:35.629 --> 00:16:38.210 That's a powerful testament to his belief in 00:16:38.210 --> 00:16:40.830 the empirical truth of what he'd found. He knew 00:16:40.830 --> 00:16:43.789 he was right. To understand why he was so revolutionary, 00:16:44.110 --> 00:16:46.610 we need to spend a moment on that dominant theory 00:16:46.610 --> 00:16:50.169 he was up against. Blending inheritance. Why 00:16:50.169 --> 00:16:52.909 was that idea so intuitive to everyone? It seems 00:16:52.909 --> 00:16:55.570 obvious, right? It does. For many characteristics, 00:16:55.909 --> 00:16:58.750 like human height or weight or skin color, the 00:16:58.750 --> 00:17:00.870 offspring often appear to be an average of the 00:17:00.870 --> 00:17:03.210 parents. If you mix red paint and white paint, 00:17:03.269 --> 00:17:06.079 you get pink. It seems to perfectly explain what 00:17:06.079 --> 00:17:08.880 we see. But it has a fatal flaw, especially for 00:17:08.880 --> 00:17:11.859 evolution. A fatal flaw. Blending constantly 00:17:11.859 --> 00:17:15.099 reduces variation. If everyone blends with everyone 00:17:15.099 --> 00:17:17.359 else, eventually everyone looks the same. And 00:17:17.359 --> 00:17:19.440 that removes the raw material, the variation 00:17:19.440 --> 00:17:22.000 that natural selection needs to work on. And 00:17:22.000 --> 00:17:24.099 Darwin knew this was a problem, so he proposed 00:17:24.099 --> 00:17:26.839 his own theory of pangenesis. Pangenesis was 00:17:26.839 --> 00:17:29.230 a really... It was an unsuccessful attempt to 00:17:29.230 --> 00:17:32.069 solve this. Darwin hypothesized that these tiny 00:17:32.069 --> 00:17:34.710 particles, called genules, were shed by all parts 00:17:34.710 --> 00:17:36.549 of the body and collected in the reproductive 00:17:36.549 --> 00:17:39.490 organs, passing traits on. It was a very complex 00:17:39.490 --> 00:17:42.069 and ultimately wrong attempt to explain inheritance 00:17:42.069 --> 00:17:44.630 without the concept of discrete, non -blending 00:17:44.630 --> 00:17:47.069 factors. It just shows how badly the scientific 00:17:47.069 --> 00:17:49.829 world needed Mendel. And we should look at Mendel's 00:17:49.829 --> 00:17:52.579 own struggles beyond the pea plant. Because while 00:17:52.579 --> 00:17:55.140 the peas yielded these crystalline perfect results, 00:17:55.460 --> 00:17:58.279 his experiments with hawkweed, haricium, the 00:17:58.279 --> 00:18:00.839 plant Nagley suggested. They were a total mess. 00:18:01.039 --> 00:18:03.740 A total mess. The results were confusing and 00:18:03.740 --> 00:18:06.440 variable. The inheritance patterns didn't follow 00:18:06.440 --> 00:18:09.799 his precise ratios at all. It was a genuine setback 00:18:09.799 --> 00:18:12.539 for him, and it likely contributed to Nagley's 00:18:12.539 --> 00:18:14.640 skepticism. He had the right methodology, but 00:18:14.640 --> 00:18:17.779 just the wrong organism. Exactly. The irony is 00:18:17.779 --> 00:18:20.880 so rich. The confusion was only resolved long 00:18:20.880 --> 00:18:23.279 after his death when it was discovered that many 00:18:23.279 --> 00:18:26.579 hawkweed species are apomyctic. Meaning they 00:18:26.579 --> 00:18:29.460 produce sieves through an asexual process. Right. 00:18:29.519 --> 00:18:31.400 They essentially clone the mother plant. So the 00:18:31.400 --> 00:18:33.660 standard rules of sexual inheritance, like segregation 00:18:33.660 --> 00:18:35.660 and independent assortment, they just do not 00:18:35.660 --> 00:18:38.039 apply. He was dealing with an organism that fundamentally 00:18:38.039 --> 00:18:40.579 defied the rules he himself had just discovered. 00:18:40.740 --> 00:18:43.529 Wow. Had he started with Hawkweed, he might never 00:18:43.529 --> 00:18:45.789 have published his theory at all. It was a huge 00:18:45.789 --> 00:18:47.970 stroke of scientific luck that he began with 00:18:47.970 --> 00:18:50.309 Pesum Sacivum. We should also just briefly touch 00:18:50.309 --> 00:18:52.900 on the full scope of his work. While we focus 00:18:52.900 --> 00:18:55.539 on the peas, most of his published papers actually 00:18:55.539 --> 00:18:58.059 related to meteorology. That's right. He was 00:18:58.059 --> 00:19:01.480 highly systematic. He founded the Austrian Meteorological 00:19:01.480 --> 00:19:05.220 Society in 1865, and he kept meticulous records 00:19:05.220 --> 00:19:08.299 on atmospheric conditions, sunspots, all of it. 00:19:08.339 --> 00:19:10.660 It just shows his commitment to quantitative 00:19:10.660 --> 00:19:13.740 observation across all fields of natural science. 00:19:13.859 --> 00:19:16.559 And, of course, his other great love, beekeeping. 00:19:16.700 --> 00:19:19.880 The bees. He bred them in custom -designed hives 00:19:19.880 --> 00:19:22.579 using particularly aggressive Cyprian and Carniolan 00:19:22.579 --> 00:19:25.460 varieties, which apparently annoy the other monks 00:19:25.460 --> 00:19:27.799 and monastery visitors quite a bit. I love that 00:19:27.799 --> 00:19:29.940 detail. He called them my dearest little animals. 00:19:30.039 --> 00:19:33.240 It adds this layer of human warmth to the meticulous 00:19:33.240 --> 00:19:35.119 scientist. But the fact that he was asked to 00:19:35.119 --> 00:19:36.599 get rid of them because they were too aggressive 00:19:36.599 --> 00:19:39.619 shows that maybe his enthusiasm sometimes ran 00:19:39.619 --> 00:19:41.960 a little ahead of monastery harmony. And we should 00:19:41.960 --> 00:19:44.680 also definitively put one persistent myth to 00:19:44.680 --> 00:19:47.619 rest. The mouse story. The mouse story. The story 00:19:47.619 --> 00:19:49.859 that Mendel only switched from breeding mice 00:19:49.859 --> 00:19:52.920 to plants because the abbot declared that observing 00:19:52.920 --> 00:19:55.740 rodent sex was unseemly for a priest? That's 00:19:55.740 --> 00:19:58.380 just not accurate. No. The abbot at the time, 00:19:58.440 --> 00:20:01.400 Abbot Knapp, personally oversaw sheep breeding 00:20:01.400 --> 00:20:04.819 on the monastery estate. They were not prudish 00:20:04.819 --> 00:20:07.740 about animal husbandry. Mendel's focus shifted 00:20:07.740 --> 00:20:09.880 to plants for scientific reasons, because they 00:20:09.880 --> 00:20:12.980 were a better model organism for producing clear, 00:20:13.220 --> 00:20:16.420 quantifiable results, not because of some clerical 00:20:16.420 --> 00:20:18.880 modesty. Okay, this is the section where the 00:20:18.880 --> 00:20:22.000 story moves from historical oversight to, well... 00:20:22.200 --> 00:20:25.779 intellectual scandal. Mendel died in 1884, largely 00:20:25.779 --> 00:20:28.359 unrecognized. His work is rediscovered in 1900. 00:20:28.720 --> 00:20:32.799 Fast forward another three decades to 1936. Ronald 00:20:32.799 --> 00:20:35.359 Fisher, who by this time is arguably the most 00:20:35.359 --> 00:20:37.700 important statistician and population geneticist 00:20:37.700 --> 00:20:40.099 in the world, decides to take a rigorous look 00:20:40.099 --> 00:20:42.660 at Mendel's original data. And Fisher was in 00:20:42.660 --> 00:20:44.859 a unique position to do this. He was the person 00:20:44.859 --> 00:20:47.039 who had mathematically reconciled Mendel's discrete 00:20:47.039 --> 00:20:49.220 genetics with Darwin's continuous evolution. 00:20:49.869 --> 00:20:52.269 If anyone was equipped to understand and defend 00:20:52.269 --> 00:20:55.410 Mendel's work, it was Fischer. So Fischer reconstructs 00:20:55.410 --> 00:20:57.529 Mendel's F2 generation experiments where that 00:20:57.529 --> 00:21:00.289 3 to 1 ratio should appear, and he performs a 00:21:00.289 --> 00:21:02.690 rigorous statistical analysis using the methods 00:21:02.690 --> 00:21:04.730 that he himself had pioneered. He was looking 00:21:04.730 --> 00:21:08.130 for evidence that the observed results deviated 00:21:08.130 --> 00:21:10.029 from the mathematically expected results. Which 00:21:10.029 --> 00:21:12.829 they should. Right. In any real -world experiment, 00:21:13.150 --> 00:21:15.500 statistical deviation is inevitable. You have 00:21:15.500 --> 00:21:18.140 random chance, maybe a slightly imperfect technique, 00:21:18.400 --> 00:21:20.859 environmental variables, or even just the small 00:21:20.859 --> 00:21:23.180 sample size in some of his experimental groups. 00:21:23.380 --> 00:21:26.299 All that should produce results that vary, you 00:21:26.299 --> 00:21:28.039 know, a little bit from the perfect three to 00:21:28.039 --> 00:21:30.420 one ratio. But Fisher found the exact opposite. 00:21:30.839 --> 00:21:33.279 He found that the ratio of dominant to recessive 00:21:33.279 --> 00:21:36.420 phenotypes was implausibly and consistently too 00:21:36.420 --> 00:21:39.420 close to the expected 3 to 1 ratio. His data 00:21:39.420 --> 00:21:41.980 showed almost no statistical variance. It was 00:21:41.980 --> 00:21:44.579 too clean. Way too clean. To a statistician, 00:21:44.579 --> 00:21:47.299 this is a massive red flag. It suggests that 00:21:47.299 --> 00:21:49.960 the random variation you would expect in a real 00:21:49.960 --> 00:21:52.480 -world biological system has been artificially 00:21:52.480 --> 00:21:54.819 suppressed somehow. And Fisher did not mince 00:21:54.819 --> 00:21:58.039 words. No, he did not. He asserted that the data 00:21:58.039 --> 00:22:01.140 of most, if not all, of the experiments have 00:22:01.140 --> 00:22:03.519 been falsified to agree closely with Mendel's 00:22:03.519 --> 00:22:07.019 expectations. Falsified. That is a staggering 00:22:07.019 --> 00:22:10.099 accusation. He used highly charged language, 00:22:10.420 --> 00:22:13.660 labeling the alleged observations as abominable, 00:22:13.700 --> 00:22:17.880 shocking, and, most famously, He was implying 00:22:17.880 --> 00:22:20.880 either deliberate fraud or, at a minimum, an 00:22:20.880 --> 00:22:24.880 extreme, systematic, unconscious bias that rendered 00:22:24.880 --> 00:22:28.099 the data useless for true statistical rigor. 00:22:28.359 --> 00:22:31.200 Another statistician, AWF Edwards, later captured 00:22:31.200 --> 00:22:33.460 the feeling of the statistical community perfectly. 00:22:33.740 --> 00:22:36.279 Yeah, that quote is great. He remarked, one can 00:22:36.279 --> 00:22:38.859 applaud the lucky gambler, but when he is lucky 00:22:38.859 --> 00:22:41.359 again tomorrow and the next day and the following 00:22:41.359 --> 00:22:43.759 day, one is entitled to become a little suspicious. 00:22:43.960 --> 00:22:46.720 It's the pattern of perfection repeated across 00:22:46.720 --> 00:22:49.039 multiple different experiments. That's what raises 00:22:49.039 --> 00:22:51.059 the red flag. It wasn't a one off lucky result. 00:22:51.549 --> 00:22:54.009 So on the one hand, we have this powerful statistical 00:22:54.009 --> 00:22:56.690 evidence suggesting data manipulation. But on 00:22:56.690 --> 00:22:58.230 the other hand, we have everything we know about 00:22:58.230 --> 00:23:00.809 Mendel, the man, the meticulous friar, the failed 00:23:00.809 --> 00:23:03.329 examiner, the intellectually honest correspondent 00:23:03.329 --> 00:23:06.170 suggesting integrity. And that is the Mendelian 00:23:06.170 --> 00:23:08.349 paradox. How do you resolve this contradiction 00:23:08.349 --> 00:23:11.069 between the perfect data and the good friar? 00:23:11.170 --> 00:23:13.529 There are a few competing explanations, right? 00:23:13.710 --> 00:23:16.720 Right. There are three primary explanations that 00:23:16.720 --> 00:23:19.220 attempt to resolve this intellectual knot, and 00:23:19.220 --> 00:23:21.380 each one has some pretty profound implications 00:23:21.380 --> 00:23:24.319 for how scientific discovery actually happens. 00:23:24.599 --> 00:23:26.900 Okay, let's start with the least charitable but 00:23:26.900 --> 00:23:30.059 maybe the most common explanation, confirmation 00:23:30.059 --> 00:23:33.839 bias. Confirmation bias suggests that Mendel, 00:23:33.960 --> 00:23:36.819 perhaps completely subconsciously, suffered from 00:23:36.819 --> 00:23:39.400 a bias where he unintentionally favored observations 00:23:39.400 --> 00:23:42.819 that confirmed his theoretical expectation. So 00:23:42.819 --> 00:23:45.720 he knew what the answer should be, and that colored 00:23:45.720 --> 00:23:49.240 how he counted. Exactly. Imagine a pea pod produced 00:23:49.240 --> 00:23:52.519 21 yellow seeds and 9 green ones. That's a 2 00:23:52.519 --> 00:23:56.180 .3 to 1 ratio, not 3 to 1. Maybe he noted a few 00:23:56.180 --> 00:23:58.819 of the paler yellow ones as green to nudge the 00:23:58.819 --> 00:24:02.039 total count closer to his expectation. Or, perhaps, 00:24:02.259 --> 00:24:04.500 he simply stopped counting once he reached a 00:24:04.500 --> 00:24:06.519 number that perfectly confirmed the ratio he 00:24:06.519 --> 00:24:08.789 already knew was correct. So he's not consciously 00:24:08.789 --> 00:24:11.289 committing fraud, but his knowledge is subtly 00:24:11.289 --> 00:24:13.630 corrupting the objectivity of his counting. That's 00:24:13.630 --> 00:24:16.230 the idea. But there's a more complex, almost 00:24:16.230 --> 00:24:18.289 ethical justification that some scholars have 00:24:18.289 --> 00:24:20.309 offered. And what's that? This theory suggests 00:24:20.309 --> 00:24:22.490 a conscious simplification for the sake of a 00:24:22.490 --> 00:24:24.930 breakthrough. You have to remember his context. 00:24:25.470 --> 00:24:28.150 Mendel was an obscure working class innovator 00:24:28.150 --> 00:24:32.089 trying to communicate a radically new, counterintuitive 00:24:32.089 --> 00:24:36.369 idea. particulate inheritance to an elite, skeptical 00:24:36.369 --> 00:24:38.450 audience that was completely committed to the 00:24:38.450 --> 00:24:41.190 idea of blending. He had to, as one historian 00:24:41.190 --> 00:24:43.809 put it, break through the cognitive paradigms 00:24:43.809 --> 00:24:46.670 and social prejudices of his time. And the argument 00:24:46.670 --> 00:24:48.809 goes that Mendel might have looked at his raw, 00:24:48.930 --> 00:24:52.410 messy, yet fundamentally correct data and decided 00:24:52.410 --> 00:24:54.529 that the larger imperative was ensuring his revolutionary 00:24:54.529 --> 00:24:57.539 theory was heard. So if the raw data, with all 00:24:57.539 --> 00:24:59.940 its normal statistical noise, was too messy or 00:24:59.940 --> 00:25:02.220 complicated for a hostile audience... It might 00:25:02.220 --> 00:25:04.279 have doomed the theory to obscurity for another 00:25:04.279 --> 00:25:06.680 generation. So maybe he made a calculated choice 00:25:06.680 --> 00:25:09.619 to simplify or polish the data to make the underlying 00:25:09.619 --> 00:25:12.480 truth of that 3 to 1 ratio absolutely undeniable 00:25:12.480 --> 00:25:14.539 and palatable to his readers. That perspective 00:25:14.539 --> 00:25:17.299 is fascinating. It turns the supposed flaw into 00:25:17.299 --> 00:25:19.579 an act of calculated altruism for the advancement 00:25:19.579 --> 00:25:22.920 of science. It's a very thorny ethical dilemma. 00:25:23.460 --> 00:25:27.359 It asks... Can a scientist be statistically dishonest 00:25:27.359 --> 00:25:30.180 in the short term to ensure a conceptual truth 00:25:30.180 --> 00:25:32.779 prevails in the long term? A tough question. 00:25:33.059 --> 00:25:35.400 But we have to remember that this narrative is 00:25:35.400 --> 00:25:37.960 also challenged. Not everyone buys it. Right. 00:25:38.039 --> 00:25:40.240 That brings us to the third explanation, which 00:25:40.240 --> 00:25:42.900 is the full rebuttal to Fisher's accusation, 00:25:42.980 --> 00:25:45.960 led by modern geneticists like Daniel Hartle 00:25:45.960 --> 00:25:48.000 and Daniel Fairbanks. And what's their argument? 00:25:48.319 --> 00:25:52.109 They argue that Fisher for all his genius, fundamentally 00:25:52.109 --> 00:25:55.130 misinterpreted a key aspect of Mendel's experimental 00:25:55.130 --> 00:25:58.210 design. They argue that Fisher made certain assumptions 00:25:58.210 --> 00:26:00.750 about how Mendel collected his data that might 00:26:00.750 --> 00:26:03.390 be wrong. For instance? For instance, they suggest 00:26:03.390 --> 00:26:05.910 that Mendel likely scored more than 10 progeny 00:26:05.910 --> 00:26:08.230 per test for certain categories, which would 00:26:08.230 --> 00:26:11.190 change the statistical expectations. A subtle 00:26:11.190 --> 00:26:13.730 change in the sample size or the scoring methodology, 00:26:13.950 --> 00:26:15.849 which Fisher could not have confirmed because 00:26:15.849 --> 00:26:18.509 the raw data was lost, would drastically alter 00:26:18.509 --> 00:26:20.869 the statistics. And it would essentially dissolve 00:26:20.869 --> 00:26:23.690 much of that alleged statistical imbalance. Their 00:26:23.690 --> 00:26:26.549 conclusion is pretty definitive. They say that 00:26:26.549 --> 00:26:28.670 Fisher's allegation of deliberate falsification 00:26:28.670 --> 00:26:31.369 can finally be put to rest because the claim 00:26:31.369 --> 00:26:35.009 is unsupported by convincing evidence when you 00:26:35.009 --> 00:26:37.569 interpret Mendel's methods through the lens of 00:26:37.569 --> 00:26:40.569 a meticulous early statistician rather than a 00:26:40.569 --> 00:26:42.750 modern one. So the data is still astonishingly 00:26:42.750 --> 00:26:45.549 good, but it might not be quite as cooked as 00:26:45.549 --> 00:26:47.970 Fisher originally claimed. That's their argument. 00:26:48.329 --> 00:26:50.250 And the fact that this debate is still going 00:26:50.250 --> 00:26:52.809 on is a testament to Mendel's profound legacy. 00:26:53.309 --> 00:26:57.269 A man who published his findings in 1866 is still 00:26:57.269 --> 00:27:00.150 generating vigorous statistical debate among 00:27:00.150 --> 00:27:02.410 the world's leading geneticists and mathematicians 00:27:02.410 --> 00:27:04.990 a century and a half later. So that 35 -year 00:27:04.990 --> 00:27:07.750 sleep finally ended with a bang at the turn of 00:27:07.750 --> 00:27:10.119 the 20th century. Mendel's importance was realized 00:27:10.119 --> 00:27:12.220 through this simultaneous, independent awakening 00:27:12.220 --> 00:27:15.259 across three different countries. Yes. The 1900 00:27:15.259 --> 00:27:17.460 reawakening was triggered by researchers who 00:27:17.460 --> 00:27:20.220 were seeking to understand the nature of discontinuous 00:27:20.220 --> 00:27:22.940 inheritance, the very mechanism Mendel had described. 00:27:23.299 --> 00:27:26.440 They needed discrete, non -blending units to 00:27:26.440 --> 00:27:28.240 explain the variation they were seeing in their 00:27:28.240 --> 00:27:30.470 own work. And this search led to the independent 00:27:30.470 --> 00:27:32.769 duplication of Mendel's pea plant experiments 00:27:32.769 --> 00:27:35.769 by three scientists, all of whom published their 00:27:35.769 --> 00:27:37.930 findings within a two -month span in the spring 00:27:37.930 --> 00:27:41.309 of 1900. Hugo de Vries in the Netherlands, Karl 00:27:41.309 --> 00:27:44.009 Korens in Germany, and Erich von Schermack in 00:27:44.009 --> 00:27:46.930 Austria. And the scientific integrity of the 00:27:46.930 --> 00:27:49.769 era is really evident here, because both de Vries 00:27:49.769 --> 00:27:52.789 and Korens explicitly acknowledged Mendel's priority. 00:27:53.069 --> 00:27:55.349 They gave the credit back to the humble friar 00:27:55.349 --> 00:27:58.529 whose work they had unknowingly replicated. Yeah, 00:27:58.549 --> 00:28:00.470 while Shermak's depth of understanding of the 00:28:00.470 --> 00:28:03.509 laws is now sometimes disputed, the impact of 00:28:03.509 --> 00:28:05.849 those three publications was immediate and dramatic. 00:28:06.190 --> 00:28:08.950 The scientific world finally realized that Mendel 00:28:08.950 --> 00:28:11.369 had offered a genotypic understanding of heredity, 00:28:11.430 --> 00:28:14.630 that underlying factor, the big Y, little b structure, 00:28:14.950 --> 00:28:17.250 that previous studies, which had only focused 00:28:17.250 --> 00:28:19.970 on the observable phenotype, had lacked but this 00:28:19.970 --> 00:28:21.950 rediscovery didn't lead to universal acceptance 00:28:21.950 --> 00:28:24.670 it immediately fueled a massive intellectual 00:28:24.670 --> 00:28:27.690 conflict that really defined early 20th century 00:28:27.690 --> 00:28:30.150 biology the war between the mendelians and the 00:28:30.150 --> 00:28:33.789 biometricians the mendelians led by william bateson 00:28:33.789 --> 00:28:36.130 who coined the term genetics and established 00:28:36.130 --> 00:28:38.829 much of the modern terminology they were all 00:28:38.829 --> 00:28:41.589 about these clear discrete units of inheritance 00:28:41.589 --> 00:28:44.569 they were all about the three to one ratio and 00:28:44.569 --> 00:28:47.130 clear qualitative differences. Conversely, the 00:28:47.130 --> 00:28:49.789 biometricians, led by figures like Carl Pearson 00:28:49.789 --> 00:28:53.549 and W .F .R. Weldon, focused on statistical rigor 00:28:53.549 --> 00:28:57.089 and the analysis of continuous, subtle phenotype 00:28:57.089 --> 00:29:00.049 variation like height and weight. And they found 00:29:00.049 --> 00:29:02.589 Mendel's neat, discrete categories simplistic. 00:29:03.259 --> 00:29:05.640 They argued that life was too complex for simple 00:29:05.640 --> 00:29:08.059 three -to -one ratios. They thought the Mendelians 00:29:08.059 --> 00:29:10.700 were being naive. It was a fierce academic battle. 00:29:10.859 --> 00:29:13.519 One side had a clean, simple mechanism, and the 00:29:13.519 --> 00:29:15.700 other side had superior statistical methods for 00:29:15.700 --> 00:29:18.339 analyzing entire populations. And in a supreme 00:29:18.339 --> 00:29:21.140 historical irony, the two warring camps were 00:29:21.140 --> 00:29:23.059 ultimately reconciled through the work of R .A. 00:29:23.059 --> 00:29:25.480 Fisher. The same statistician who later accused 00:29:25.480 --> 00:29:28.880 Mendel of cooking his data. The very same. Starting 00:29:28.880 --> 00:29:31.259 around 1918, Fisher mathematically proved that 00:29:31.259 --> 00:29:34.220 continuous variation, like height, could be explained 00:29:34.220 --> 00:29:36.420 by the cumulative action of multiple Mendelian 00:29:36.420 --> 00:29:38.539 factors working together. So both sides were 00:29:38.539 --> 00:29:41.079 right. Exactly. And this successful synthesis 00:29:41.079 --> 00:29:43.799 of genetics and biometrics led directly to the 00:29:43.799 --> 00:29:46.039 modern synthesis of evolutionary biology in the 00:29:46.039 --> 00:29:49.319 1930s and 40s, finally integrating Mendelian 00:29:49.319 --> 00:29:51.720 genetics with Darwin's natural selection theory 00:29:51.720 --> 00:29:54.319 and establishing the framework for biology that 00:29:54.319 --> 00:29:56.599 we still use today. Now, before we get to the 00:29:56.599 --> 00:29:59.000 modern molecular age, it's worth briefly noting 00:29:59.000 --> 00:30:01.519 the tragic rejection of this science in certain 00:30:01.519 --> 00:30:04.559 political regimes. Yes. In the mid -20th century, 00:30:04.740 --> 00:30:06.720 particularly in the Soviet Union under Stalin 00:30:06.720 --> 00:30:09.500 and later in Maoist China, Mendelian genetics 00:30:09.500 --> 00:30:12.779 was forcibly rejected. It was outlawed. In favor 00:30:12.779 --> 00:30:15.980 of a state -mandated pseudoscience known as Lamarckism 00:30:15.980 --> 00:30:20.240 or Lysenkoism. This ideological rejection which 00:30:20.240 --> 00:30:22.099 claimed that acquired characteristics could be 00:30:22.099 --> 00:30:24.460 inherited and that genetics was a bourgeois science, 00:30:24.700 --> 00:30:26.960 led to the imprisonment and execution of real 00:30:26.960 --> 00:30:29.619 geneticists. And it resulted in disastrous agricultural 00:30:29.619 --> 00:30:32.299 policies that contributed to severe famines in 00:30:32.299 --> 00:30:34.940 both nations. It's a stark reminder of the profound 00:30:34.940 --> 00:30:37.380 real -world consequences of ignoring established 00:30:37.380 --> 00:30:40.079 scientific law for political reasons. Coming 00:30:40.079 --> 00:30:42.500 back to the science, though, the final, ultimate 00:30:42.500 --> 00:30:45.460 vindication of Mendel's invivible factors is 00:30:45.460 --> 00:30:48.190 the modern molecular proof. We know those factors 00:30:48.190 --> 00:30:51.450 are genes, stretches of DNA. And the effort to 00:30:51.450 --> 00:30:54.670 physically identify and map these specific genes 00:30:54.670 --> 00:30:57.190 responsible for the seven traits Mendel studied 00:30:57.190 --> 00:30:59.910 that took over a century. It's an incredible 00:30:59.910 --> 00:31:03.490 timeline. Mendel laid down the law in the 1860s, 00:31:03.490 --> 00:31:06.069 but the scientific world didn't finish the molecular 00:31:06.069 --> 00:31:08.750 confirmation until just recently. How recently? 00:31:09.109 --> 00:31:12.150 In fact, it was only in 2025 that the last three 00:31:12.150 --> 00:31:14.089 of the seven genes responsible for the traits 00:31:14.089 --> 00:31:17.150 Mendel observed were finally identified and mapped 00:31:17.150 --> 00:31:19.690 within the pea genome. So a complete molecular 00:31:19.690 --> 00:31:22.509 map of the seven traits defined by a friar in 00:31:22.509 --> 00:31:24.690 his garden was only finished now. That's amazing. 00:31:24.890 --> 00:31:27.170 It really is. And looking at the specific molecular 00:31:27.170 --> 00:31:29.710 realities just brings his abstract observations 00:31:29.710 --> 00:31:32.359 to life. Okay, give us an example. He observed 00:31:32.359 --> 00:31:35.059 the wrinkled phenotype, the irregularly shaped 00:31:35.059 --> 00:31:37.700 seed. What causes that at a molecular level? 00:31:37.880 --> 00:31:40.019 We now know that it's caused by an insertion 00:31:40.019 --> 00:31:43.359 of a foreign piece of DNA into the PSSBE1 gene. 00:31:43.579 --> 00:31:46.420 And what does that gene do? PSSBE1 codes for 00:31:46.420 --> 00:31:48.299 an enzyme called starch -branching enzyme 1. 00:31:48.700 --> 00:31:51.339 The insertion inactivates this enzyme. Without 00:31:51.339 --> 00:31:53.700 it, the pea plant can't properly convert sugar 00:31:53.700 --> 00:31:55.920 into starch, causing the seeds to accumulate 00:31:55.920 --> 00:31:58.779 water, shrink when they dry, and thus wrinkle. 00:31:59.079 --> 00:32:01.920 So Mendel was measuring the macroscopic result 00:32:01.920 --> 00:32:05.400 of a single molecular insertional mutation. Precisely. 00:32:05.400 --> 00:32:08.019 And the yellow seed color he tracked so closely, 00:32:08.180 --> 00:32:10.680 the dominant one, that's caused by a mutation 00:32:10.680 --> 00:32:14.599 in the PSSGR gene. That's GR. PSSGR stands for 00:32:14.599 --> 00:32:16.880 state green. It's a gene that typically breaks 00:32:16.880 --> 00:32:19.079 down chlorophyll to reveal the yellow pigments 00:32:19.079 --> 00:32:21.680 underneath. If that gene is mutated and fails, 00:32:21.920 --> 00:32:24.500 as happens in the dominant yellow pea, the chlorophyll 00:32:24.500 --> 00:32:26.720 degradation is inhibited and the yellow color 00:32:26.720 --> 00:32:29.059 is exposed. What about flower color? The white 00:32:29.059 --> 00:32:31.319 flower phenotype, a classic recessive trait, 00:32:31.519 --> 00:32:34.599 is caused by a large deletion in the PSBHLH gene. 00:32:35.000 --> 00:32:37.259 This gene is necessary for producing the purple 00:32:37.259 --> 00:32:40.220 pigment, anthocyanin. No gene, no purple, so 00:32:40.220 --> 00:32:41.980 the flowers are white. And even plant height, 00:32:42.079 --> 00:32:44.660 which he described as either tall or dwarf. That's 00:32:44.660 --> 00:32:49.180 caused by the PSGA3OX1 gene. This gene is crucial 00:32:49.180 --> 00:32:51.880 for synthesizing the plant growth hormone jabrilin. 00:32:52.079 --> 00:32:55.480 The dwarf plants, the recessives, have a mutation 00:32:55.480 --> 00:32:57.420 that stops the hormone production so they don't 00:32:57.420 --> 00:33:00.380 grow tall. These molecular discoveries just validate 00:33:00.380 --> 00:33:03.059 with absolute certainty that his quantitative 00:33:03.059 --> 00:33:06.859 model was mapping real physical biological entities. 00:33:08.039 --> 00:33:10.140 After this incredible journey, what happened 00:33:10.140 --> 00:33:12.400 to the man who gave us this blueprint? Mendel 00:33:12.400 --> 00:33:15.539 died in 1884, still embroiled in those tax disputes. 00:33:15.839 --> 00:33:18.400 And in a final tragic irony related to those 00:33:18.400 --> 00:33:20.940 disputes, the succeeding Abbott, worried about 00:33:20.940 --> 00:33:22.640 potential governmental scrutiny and intervention, 00:33:22.960 --> 00:33:25.440 burned all of Mendel's personal and scientific 00:33:25.440 --> 00:33:27.779 papers. He burned them. He burned them. He wanted 00:33:27.779 --> 00:33:29.680 to close the book on the previous administration's 00:33:29.680 --> 00:33:32.019 affairs. We lost decades of scientific records, 00:33:32.099 --> 00:33:34.140 potentially those very raw data sheets that might 00:33:34.140 --> 00:33:36.440 have resolved the statistical paradox once and 00:33:36.440 --> 00:33:39.000 for all. But his posthumous legacy is now immense. 00:33:39.359 --> 00:33:42.720 In 2021, for his 200th birthday, his body was 00:33:42.720 --> 00:33:45.380 exhumed. Right. And scientists analyzed his genome, 00:33:45.519 --> 00:33:47.519 revealing that he had a predisposition to heart 00:33:47.519 --> 00:33:50.619 problems and confirming his body height at 168 00:33:50.619 --> 00:33:53.279 centimeters. And he's commemorated globally now. 00:33:53.400 --> 00:33:56.039 There's a Mount Mendel in New Zealand, the Mendel 00:33:56.039 --> 00:33:59.000 Polar Station in Antarctica. His time did indeed 00:33:59.000 --> 00:34:02.079 come, but only long after he was gone. What a 00:34:02.079 --> 00:34:04.170 journey we've charted today. From the financially 00:34:04.170 --> 00:34:06.589 struggling gardener whose sister sacrificed her 00:34:06.589 --> 00:34:09.269 dowry, through the seven meticulous years in 00:34:09.269 --> 00:34:11.889 the garden, to the statistical paradox that still 00:34:11.889 --> 00:34:14.909 challenges his integrity, and finally, the ultimate 00:34:14.909 --> 00:34:17.150 molecular proof that arrived just a few years 00:34:17.150 --> 00:34:20.409 ago. Gregor Mendel's ultimate success really 00:34:20.409 --> 00:34:23.949 validates his belief, my time will come. His 00:34:23.949 --> 00:34:26.329 work proves the power of systematic mathematical 00:34:26.329 --> 00:34:29.139 observation. even when you're operating outside 00:34:29.139 --> 00:34:31.420 the scientific establishment. The ultimate knowledge 00:34:31.420 --> 00:34:34.219 nugget here, for me, is that incredible juxtaposition 00:34:34.219 --> 00:34:37.420 of historical oversight and modern clarity. He 00:34:37.420 --> 00:34:39.619 defined his factors, the basic units of life, 00:34:39.780 --> 00:34:42.619 in the 1860s with a theory that Darwin missed 00:34:42.619 --> 00:34:45.260 completely. Yet it took us until the year 2025, 00:34:45.840 --> 00:34:48.400 a century and a half later, to fully identify 00:34:48.400 --> 00:34:50.739 the molecular location and mechanism of the seven 00:34:50.739 --> 00:34:53.420 simple traits he was tracking. He saw the consequence 00:34:53.420 --> 00:34:55.500 long, long before we could ever see the cause. 00:34:55.920 --> 00:34:58.000 And that brings us back to that central mystery, 00:34:58.300 --> 00:35:01.260 the Mendelian paradox. We discussed the theory 00:35:01.260 --> 00:35:04.179 that Mendel, an obscure genius, might have felt 00:35:04.179 --> 00:35:06.659 compelled to simplify his data just slightly 00:35:06.659 --> 00:35:09.539 to ensure his revolutionary and ultimately correct 00:35:09.539 --> 00:35:12.360 theory of inheritance was heard and accepted 00:35:12.360 --> 00:35:16.219 by a rigid, skeptical scientific world. It forces 00:35:16.219 --> 00:35:18.860 you to consider a really difficult choice. If 00:35:18.860 --> 00:35:20.780 your statistical evidence is technically flawed, 00:35:20.980 --> 00:35:23.039 but your underlying scientific conclusion is 00:35:23.039 --> 00:35:25.920 conceptually true and leads to a revolution in 00:35:25.920 --> 00:35:28.639 understanding, what's the right path for an innovator? 00:35:28.739 --> 00:35:31.320 Does the quest for acceptance, the moral imperative 00:35:31.320 --> 00:35:34.019 of advancing scientific knowledge, sometimes 00:35:34.019 --> 00:35:36.420 justify actions that challenge strict scientific 00:35:36.420 --> 00:35:38.579 objectivity? That is a deep dive for another 00:35:38.579 --> 00:35:38.820 day.