Okay, let's unpack this. We are opening up the
story of the man whose name is synonymous with
the very blueprint of life, Gregor Mendel. He
was a quiet, perpetually struggling Austrian
friar who, using nothing more than, you know,
pea plants and some pretty rigorous mathematics,
unlocked the fundamental laws of heredity. We're
talking about the father of modern genetics.
It's a title he absolutely earned, but the story
of how he earned it and how long it took for
the world to notice is just incredible. It's
an incredible story of delayed recognition for
sure. So between 1856 and 1863, Mendel conducts
the experiments that establish the fundamental
rules of heredity. Right. And our mission today
is to really get into how he did that, and maybe
more importantly, why the scientific community
just... ignored him for 35 years. 35 years. I
mean, that's a profound intellectual lag in biology.
The whole field was basically waiting for his
discovery. It was. But the real hook here, the
thing that still gets debated today, is the paradox
baked right into his data. Yeah, this is the
really juicy part. Before anyone even had a concept
of DNA, Mendel just posits the existence of these
invisible factors, what we now call genes, and
uses them to predict traits with, well, Stunning
accuracy. And that's the tension. That's the
core of it. How could a humble monk working without
any modern equipment produce results that were
so mathematically perfect that when a top tier
statistician analyzed them in the 1930s. A giant
of the field. A giant. Yes. Ronald Fisher. He
looked at the data and flagged it as being, and
this is the quote, implausibly and consistently
too close to the expected ratios. So too perfect
to be true. Exactly. It's the Mendelian paradox,
and it's the mystery at the core of this deep
dive. We have to decide, or at least explore.
Was he the luckiest scientist who ever lived
or did he maybe feel compelled to massage the
numbers a little to make sure his revolutionary
theory was heard? To really appreciate the scale
of Mendel's achievement, I think we have to start
with his origins. This wasn't a man born into
the aristocratic scientific elite of Europe.
Not at all. He was born Johann Mendel in 1822
in Heinzendorf by Odrau, which was then the Salesian
part of the Austrian Empire. And his background
was profoundly humble, agrarian. Absolutely.
He came from a German -speaking farming family,
and that farm had been in their family for at
least 130 years. His early life was just characterized
by working the soil. He was an active gardener,
and he studied beekeeping really early on. That
practical, hands -on connection to agriculture
is so key, I think, to his later success. He
wasn't just an abstract thinker. But the path
from that farm to a university, I mean, it was
agonizingly difficult. And it really all came
down to money. He struggled constantly. Through
his studies at the gymnasium in Trappau and later
at the Philosophical Institute of the University
of Alamook, it was a constant battle. The sources
really show the financial strain was crippling.
It wasn't just a challenge. It was an existential
threat to his education. He was constantly plagued
by illness, partly from overwork and stress,
and it forced him to take time off multiple times.
When you read accounts of his early years, the
anxiety is just relentless. And education was
this luxury that he perpetually risked losing.
And the family sacrifice involved is just staggering.
It wasn't just his own effort. Right. His younger
sister, Teresa, this part of the story always
gets me. She was so committed to his education
that she actually gave him her dowry so he could
continue his studies. Think about that. That's
not just support. That is an active foundational
investment in his future. Yeah. It shows how
much faith his family had in him. Absolutely.
And this level of, well, desperation and family
support is the critical context for his next
move. Which was becoming a monk. He took the
name Gregor when he entered the Augustinian St.
Thomas's Abbey in Brno. And he did this partly
because the monastery offered intellectual sanctuary
and... crucially a way to get an education without
the financial burden. So it wasn't a purely spiritual
calling, at least not at first. It was a profound
escape from what he himself described as the
perpetual anxiety about a means of livelihood.
The monastery provided stability. It gave him
the intellectual freedom that a struggling farmer's
son otherwise could never have afforded. That
detail just makes him so much more relatable.
It does. And you have to understand, the Augustinian
order in Brno was far from being some quiet purely
spiritual retreat. It was known as a center of
intellectual life and scientific inquiry. Really?
Oh, yeah. They valued teaching, research, and
engagement with the natural sciences. The abbot
at the time, Cyril Knapp, was a huge proponent
of scientific investigation. It was the perfect
place for a mathematically inclined, nature -loving
individual like Mendel to land. So he gets there,
but he doesn't just walk into a lab and start
planting peas. No. Not at all. He was assigned
as a substitute high school teacher. And interestingly,
his primary focus after returning from his studies
at the University of Vienna was physics. And
he studied under the famous Christian Doppler.
Yes, the Doppler of the Doppler effect. This
is a crucial point that so often gets missed
in the biology textbooks. Mendel's expertise
was primarily quantitative and observational.
It was rooted in physics and meteorology, not
pure botany. So he viewed the natural world as
a system of measurable, quantifiable laws. Exactly.
And that explains why his approach to the pea
plants was so mathematical, so different from
the descriptive, qualitative botany that was
common at the time. But here's where the personal
struggle continues. And I find this detail strangely
comforting for anyone who's ever felt like an
imposter. The exam. The exam. Despite the genius
he would later display, Mendel failed the oral
portion of the certified high school teacher
exam. Not once. Not once, but twice. In 1850
and again in 1856. Can you imagine? You're an
innovator so far ahead of your time that you
literally fail the standardized test for the
job you are about to redefine. It just speaks
volumes about the disconnect between formal assessment
and true intellectual breakthrough. The system
couldn't measure what he was capable of doing.
But he had mentors. People who saw past those
exam results. We know his physics teacher, Friedrich
Franz, was key in recommending him to the Abbey
in the first place. And then there was Johann
Karl Nessler. Right. Nessler headed natural history
at Almach and had already been conducting his
own research on hereditary traits in sheep and
plants. This wasn't happening in a complete vacuum.
So there was an existing, if kind of primitive,
tradition of studying heredity within the Abbey's
intellectual sphere. Definitely. And people like
Alexander Zawadzki also encouraged his research
in Brano, possibly helping him refine his experimental
design. He was building on something. So he has
the mathematical rigor from physics. the agricultural
background from his childhood, and the support
of the abbey's intellectual environment. That
all sets the stage perfectly for his seven years
in the garden. But that scientific career, as
we know, was ultimately temporary. It had an
expiration date. Unfortunately so. In 1867, he
succeeded the long -serving abbot Cyril Frontichet
Knapp, and after officially becoming abbot in
1868, his scientific work largely just ground
to a halt. The administrative duties completely
swallowed his time. It's a classic story. He
traded his trowel and his observation notes for
accounting ledgers and legal briefs. He became
immediately and heavily burdened with these duties,
especially one serious, all -consuming dispute
with the civil government. The tax dispute. The
tax dispute, yeah. Overimposing special taxes
on religious institutions. And that fight consumed
the last decade and a half of his life. He felt
it was his duty to protect the Abbeys' intellectual
and financial independence from what he saw as
excessive state interference. It was a noble
cause, for sure, but it meant the world lost
access to one of its greatest scientific minds
prematurely. He died in 1884 from chronic nephritis,
a life cut short by stress and, you know, maybe
the sheer weight of his responsibilities as Abbot.
Okay, let's turn now to the work that defines
him. Those seven years between 1856 and 1863.
This period, spent in the monastery's substantial
two -hectare garden. That's nearly five acres.
It's a serious plot of land. This period yielded
the very foundation of modern biology. And Mendel's
success hinged on two things. His choice of organism
and his methodology. He chose the garden pea,
pisum sativum. Why peas? What was so special
about them? Well, the pea plant is scientifically
ideal for a few reasons. Yeah. First, it naturally
self -colonates, which means you can easily get
pure, true breeding lines. But you could also
easily cross -pollinate them manually, which
gives you complete control over the experiments.
You can play God, basically. You decide who the
parents are. Exactly. And the scale of his work,
again, it just speaks to his dedication. This
was painstaking work over seven years, during
which he cultivated and tested approximately
28 ,000 plants. 28 ,000? That's not a backyard
garden project. This was a mass data collection
effort executed with systematic, almost industrial
precision. And he was focused on specific, discrete
differences. He selected seven characteristics
or traits that appeared to be inherited independently
of one another. So things like seed shape, was
it round or was it wrinkled, flower color, purple
or white, pod shape, plant height. Right. And
that selection was pure genius. Unlike other
researchers who got bogged down trying to track
complex blending traits like, say, the overall
size of a leaf, Mendel chose traits that were
clearly binary. They were either or. You're either
tall or short. Your seeds were either yellow
or green. There was no in between. And that binary
choice is what made the underlying mathematical
patterns just light off the data sheet. His initial
focus was actually on seed shape. Was it angular
or was it round? Right. So let's walk everyone
through the core mechanism because this is where
his revolutionary insight really lies. He started
with what he called true breeding plants. And
that just means that if a plant had yellow seeds
and you let it self -pollinate, all of its offspring
would also have yellow seeds, generation after
generation, a pure line. So he takes a true breeding
plant for yellow seeds and he crosses it with
a true breeding plant for green seeds. This is
the parental or pea generation cross. What happens
in the resulting first filial or F1 generation?
This is the first shocker. Every single plant
in that F1 generation produced yellow seeds.
The green trait vanished. Completely. Which flew
in the face of the prevailing theory. Totally.
If blending inheritance was correct, you should
have gotten a pale yellow or a light green seed,
some kind of average of the two parents. But
no, you got 100 % yellow. This single observation
is what led him to define the concepts of dominant
and recessive. Exactly. The yellow trait that
appeared in the F1 generation, he called that
dominant. And the green trait that disappeared,
he called that recessive. This was the proof
that traits weren't blending. They were discrete
packets of information. The green information
was still there somewhere, just masked. That
masking is the revolutionary concept. So he hypothesized
that each plant carried two factors for each
trait, one from each parent. So when he crossed
a yellow -yellow plant, let's call it big Y,
big Y, with a green, green plant, little y, little
y. Every F1 offspring inherited one big Y and
one little y, making them all big Y, little y
hybrids. Correct. And since yellow, the big Y,
is dominant, they all look yellow. The phenotype
is yellow, even though their genetic makeup,
their genotype, is hybrid. But the true predictive
power, the real evidence for his laws, came in
the next step. He allowed those F1 hybrid plants
to self -fertilize, producing the F2 generation.
And this is where the math had to be perfect.
This is where the pattern reveals itself. Because
when those big Y little y plants reproduce, they
separate their factors. That's the law of segregation.
Each reproductive cell, or gamete, carries either
the big Y factor or the little y factor, but
never both. It's essentially a 50 -50 coin flip
to decide which factor gets passed on. So if
we visualize it like shuffling two separate factors,
big Y and little y, from both the male and female
parts of the flower and then recombining them
randomly. You get four possible outcomes. You
can get big Y, big Y. You can get big Y, little
y. You can get little y, big y. Or you can get
little y, little y. And because big Y, little
y, and little y, big y are functionally the same,
they're both hybrids. And because yellow is dominant,
you end up with three possible ways to be yellow.
The purebred and the two hybrids. And only one
way to be green, the purebred recessive. Which
is how the recessive green trait reappeared in
the F2 generation. And it reappeared predictably
at that famous 3 to 1 phenotypic ratio. For every
one green pea, he counted roughly three yellow
peas. The 3 to 1 is what you see. But what you
don't see, the true invisible structure he unveiled,
is the underlying 1 to 2 to 1 genotypic ratio.
That's it. One purebred dominant, two hybrids,
and one purebred recessive. That was the conceptual
leap. He was quantifying the invisible. And that's
not even the whole picture, is it? He then showed
the law of independent assortment. Which is maybe
even more profound. It means that the inheritance
of one trait, say seed color, has absolutely
no influence on the inheritance of another trait,
like plant height. So a plant sorting out whether
it's going to be tall or short and whether its
seeds are yellow or green, those two decisions
are made completely separately. Like shuffling
two entirely different decks of cards. They don't
affect each other. And this led to even more
complex but still mathematically precise ratios
when he looked at two traits at the same time,
like the famous 9 to 3 to 3 to 1 ratio. His approach
was just unprecedented. He didn't just describe
variation. He provided a mechanism and a predictive
model for it. So he presented this monumental
work, Versucia, Uber, Flanson, Hybriden. Experiments
on Plant Hybridization at the Natural History
Society of Brno in 1865. And it was published
in their proceedings in 1866. It was effectively
the rule book for how life passed information
across generations. And yet what happened next
is one of the most agonizing footnotes in the
entire history of science. The publication of
the rule book led not to a revolution, but to
a vast deafening silence. We call this period
from 1865 to 1900. The 35 -year sleep. It's just
crushing to think about. The paper generated,
you know, a few favorable reports in local newspapers.
But that was it. That was the extent of its initial
impact. It was largely ignored by the international
scientific community. How many times was it cited?
About three times over the next three and a half
decades. That's unbelievable. So why? Why did
the world look away from such a fundamental discovery?
Well, part of the problem was how it was framed
or how it was perceived. It was seen as a paper
about hybridization. which was a common topic
for botanists rather than what it actually was,
a radical quantitative theory of inheritance.
It was too mathematical for the botanists. And
too biological for the physicists and mathematicians.
It fell right into a disciplinary crack. We see
this today as a painful example of the system
failing to recognize an obscure, highly original
innovator, especially one who was working outside
the established academic centers like Berlin
or London or Paris. And the historical consequences
of this oversight are just hard to overstate.
We know for a fact that Charles Darwin, who was
desperately trying to figure out how variation
was inherited to support his theory of natural
selection. He was completely unaware of Mendel's
work. There's a story that he had a copy of the
journal with Mendel's paper in it, but the pages
were uncut. You never read it. If Darwin had
held that paper in his hand. If he'd had that
missing piece of the puzzle that explained particulate
inheritance instead of blending, I mean, the
development of genetics and evolutionary biology
would have accelerated by decades. Oh, absolutely.
The lack of that connection is one of the great
historical tragedies of science. It's a huge
what if. And despite this global cold shoulder,
Mendel seemed to maintain this astonishing level
of internal conviction. He even corresponded
with Carl Nagelli, who was one of the most respected
botanists of the era. But Neville, who was. was
a key scientific gatekeeper at the time, he just
didn't get it. He remained skeptical. He completely
failed to appreciate the importance of Mendel's
discoveries. He was stuck in the old paradigm.
He was stuck in the blending paradigm. He actually
told Mendel to drop the peas and try his experiments
on hawkweed instead, which was a terrible suggestion.
But through all the rejection and skepticism,
Mendel reportedly told his friend, Gustav von
Niesel, that now famous line, my time will come.
That's a powerful testament to his belief in
the empirical truth of what he'd found. He knew
he was right. To understand why he was so revolutionary,
we need to spend a moment on that dominant theory
he was up against. Blending inheritance. Why
was that idea so intuitive to everyone? It seems
obvious, right? It does. For many characteristics,
like human height or weight or skin color, the
offspring often appear to be an average of the
parents. If you mix red paint and white paint,
you get pink. It seems to perfectly explain what
we see. But it has a fatal flaw, especially for
evolution. A fatal flaw. Blending constantly
reduces variation. If everyone blends with everyone
else, eventually everyone looks the same. And
that removes the raw material, the variation
that natural selection needs to work on. And
Darwin knew this was a problem, so he proposed
his own theory of pangenesis. Pangenesis was
a really... It was an unsuccessful attempt to
solve this. Darwin hypothesized that these tiny
particles, called genules, were shed by all parts
of the body and collected in the reproductive
organs, passing traits on. It was a very complex
and ultimately wrong attempt to explain inheritance
without the concept of discrete, non -blending
factors. It just shows how badly the scientific
world needed Mendel. And we should look at Mendel's
own struggles beyond the pea plant. Because while
the peas yielded these crystalline perfect results,
his experiments with hawkweed, haricium, the
plant Nagley suggested. They were a total mess.
A total mess. The results were confusing and
variable. The inheritance patterns didn't follow
his precise ratios at all. It was a genuine setback
for him, and it likely contributed to Nagley's
skepticism. He had the right methodology, but
just the wrong organism. Exactly. The irony is
so rich. The confusion was only resolved long
after his death when it was discovered that many
hawkweed species are apomyctic. Meaning they
produce sieves through an asexual process. Right.
They essentially clone the mother plant. So the
standard rules of sexual inheritance, like segregation
and independent assortment, they just do not
apply. He was dealing with an organism that fundamentally
defied the rules he himself had just discovered.
Wow. Had he started with Hawkweed, he might never
have published his theory at all. It was a huge
stroke of scientific luck that he began with
Pesum Sacivum. We should also just briefly touch
on the full scope of his work. While we focus
on the peas, most of his published papers actually
related to meteorology. That's right. He was
highly systematic. He founded the Austrian Meteorological
Society in 1865, and he kept meticulous records
on atmospheric conditions, sunspots, all of it.
It just shows his commitment to quantitative
observation across all fields of natural science.
And, of course, his other great love, beekeeping.
The bees. He bred them in custom -designed hives
using particularly aggressive Cyprian and Carniolan
varieties, which apparently annoy the other monks
and monastery visitors quite a bit. I love that
detail. He called them my dearest little animals.
It adds this layer of human warmth to the meticulous
scientist. But the fact that he was asked to
get rid of them because they were too aggressive
shows that maybe his enthusiasm sometimes ran
a little ahead of monastery harmony. And we should
also definitively put one persistent myth to
rest. The mouse story. The mouse story. The story
that Mendel only switched from breeding mice
to plants because the abbot declared that observing
rodent sex was unseemly for a priest? That's
just not accurate. No. The abbot at the time,
Abbot Knapp, personally oversaw sheep breeding
on the monastery estate. They were not prudish
about animal husbandry. Mendel's focus shifted
to plants for scientific reasons, because they
were a better model organism for producing clear,
quantifiable results, not because of some clerical
modesty. Okay, this is the section where the
story moves from historical oversight to, well...
intellectual scandal. Mendel died in 1884, largely
unrecognized. His work is rediscovered in 1900.
Fast forward another three decades to 1936. Ronald
Fisher, who by this time is arguably the most
important statistician and population geneticist
in the world, decides to take a rigorous look
at Mendel's original data. And Fisher was in
a unique position to do this. He was the person
who had mathematically reconciled Mendel's discrete
genetics with Darwin's continuous evolution.
If anyone was equipped to understand and defend
Mendel's work, it was Fischer. So Fischer reconstructs
Mendel's F2 generation experiments where that
3 to 1 ratio should appear, and he performs a
rigorous statistical analysis using the methods
that he himself had pioneered. He was looking
for evidence that the observed results deviated
from the mathematically expected results. Which
they should. Right. In any real -world experiment,
statistical deviation is inevitable. You have
random chance, maybe a slightly imperfect technique,
environmental variables, or even just the small
sample size in some of his experimental groups.
All that should produce results that vary, you
know, a little bit from the perfect three to
one ratio. But Fisher found the exact opposite.
He found that the ratio of dominant to recessive
phenotypes was implausibly and consistently too
close to the expected 3 to 1 ratio. His data
showed almost no statistical variance. It was
too clean. Way too clean. To a statistician,
this is a massive red flag. It suggests that
the random variation you would expect in a real
-world biological system has been artificially
suppressed somehow. And Fisher did not mince
words. No, he did not. He asserted that the data
of most, if not all, of the experiments have
been falsified to agree closely with Mendel's
expectations. Falsified. That is a staggering
accusation. He used highly charged language,
labeling the alleged observations as abominable,
shocking, and, most famously, He was implying
either deliberate fraud or, at a minimum, an
extreme, systematic, unconscious bias that rendered
the data useless for true statistical rigor.
Another statistician, AWF Edwards, later captured
the feeling of the statistical community perfectly.
Yeah, that quote is great. He remarked, one can
applaud the lucky gambler, but when he is lucky
again tomorrow and the next day and the following
day, one is entitled to become a little suspicious.
It's the pattern of perfection repeated across
multiple different experiments. That's what raises
the red flag. It wasn't a one off lucky result.
So on the one hand, we have this powerful statistical
evidence suggesting data manipulation. But on
the other hand, we have everything we know about
Mendel, the man, the meticulous friar, the failed
examiner, the intellectually honest correspondent
suggesting integrity. And that is the Mendelian
paradox. How do you resolve this contradiction
between the perfect data and the good friar?
There are a few competing explanations, right?
Right. There are three primary explanations that
attempt to resolve this intellectual knot, and
each one has some pretty profound implications
for how scientific discovery actually happens.
Okay, let's start with the least charitable but
maybe the most common explanation, confirmation
bias. Confirmation bias suggests that Mendel,
perhaps completely subconsciously, suffered from
a bias where he unintentionally favored observations
that confirmed his theoretical expectation. So
he knew what the answer should be, and that colored
how he counted. Exactly. Imagine a pea pod produced
21 yellow seeds and 9 green ones. That's a 2
.3 to 1 ratio, not 3 to 1. Maybe he noted a few
of the paler yellow ones as green to nudge the
total count closer to his expectation. Or, perhaps,
he simply stopped counting once he reached a
number that perfectly confirmed the ratio he
already knew was correct. So he's not consciously
committing fraud, but his knowledge is subtly
corrupting the objectivity of his counting. That's
the idea. But there's a more complex, almost
ethical justification that some scholars have
offered. And what's that? This theory suggests
a conscious simplification for the sake of a
breakthrough. You have to remember his context.
Mendel was an obscure working class innovator
trying to communicate a radically new, counterintuitive
idea. particulate inheritance to an elite, skeptical
audience that was completely committed to the
idea of blending. He had to, as one historian
put it, break through the cognitive paradigms
and social prejudices of his time. And the argument
goes that Mendel might have looked at his raw,
messy, yet fundamentally correct data and decided
that the larger imperative was ensuring his revolutionary
theory was heard. So if the raw data, with all
its normal statistical noise, was too messy or
complicated for a hostile audience... It might
have doomed the theory to obscurity for another
generation. So maybe he made a calculated choice
to simplify or polish the data to make the underlying
truth of that 3 to 1 ratio absolutely undeniable
and palatable to his readers. That perspective
is fascinating. It turns the supposed flaw into
an act of calculated altruism for the advancement
of science. It's a very thorny ethical dilemma.
It asks... Can a scientist be statistically dishonest
in the short term to ensure a conceptual truth
prevails in the long term? A tough question.
But we have to remember that this narrative is
also challenged. Not everyone buys it. Right.
That brings us to the third explanation, which
is the full rebuttal to Fisher's accusation,
led by modern geneticists like Daniel Hartle
and Daniel Fairbanks. And what's their argument?
They argue that Fisher for all his genius, fundamentally
misinterpreted a key aspect of Mendel's experimental
design. They argue that Fisher made certain assumptions
about how Mendel collected his data that might
be wrong. For instance? For instance, they suggest
that Mendel likely scored more than 10 progeny
per test for certain categories, which would
change the statistical expectations. A subtle
change in the sample size or the scoring methodology,
which Fisher could not have confirmed because
the raw data was lost, would drastically alter
the statistics. And it would essentially dissolve
much of that alleged statistical imbalance. Their
conclusion is pretty definitive. They say that
Fisher's allegation of deliberate falsification
can finally be put to rest because the claim
is unsupported by convincing evidence when you
interpret Mendel's methods through the lens of
a meticulous early statistician rather than a
modern one. So the data is still astonishingly
good, but it might not be quite as cooked as
Fisher originally claimed. That's their argument.
And the fact that this debate is still going
on is a testament to Mendel's profound legacy.
A man who published his findings in 1866 is still
generating vigorous statistical debate among
the world's leading geneticists and mathematicians
a century and a half later. So that 35 -year
sleep finally ended with a bang at the turn of
the 20th century. Mendel's importance was realized
through this simultaneous, independent awakening
across three different countries. Yes. The 1900
reawakening was triggered by researchers who
were seeking to understand the nature of discontinuous
inheritance, the very mechanism Mendel had described.
They needed discrete, non -blending units to
explain the variation they were seeing in their
own work. And this search led to the independent
duplication of Mendel's pea plant experiments
by three scientists, all of whom published their
findings within a two -month span in the spring
of 1900. Hugo de Vries in the Netherlands, Karl
Korens in Germany, and Erich von Schermack in
Austria. And the scientific integrity of the
era is really evident here, because both de Vries
and Korens explicitly acknowledged Mendel's priority.
They gave the credit back to the humble friar
whose work they had unknowingly replicated. Yeah,
while Shermak's depth of understanding of the
laws is now sometimes disputed, the impact of
those three publications was immediate and dramatic.
The scientific world finally realized that Mendel
had offered a genotypic understanding of heredity,
that underlying factor, the big Y, little b structure,
that previous studies, which had only focused
on the observable phenotype, had lacked but this
rediscovery didn't lead to universal acceptance
it immediately fueled a massive intellectual
conflict that really defined early 20th century
biology the war between the mendelians and the
biometricians the mendelians led by william bateson
who coined the term genetics and established
much of the modern terminology they were all
about these clear discrete units of inheritance
they were all about the three to one ratio and
clear qualitative differences. Conversely, the
biometricians, led by figures like Carl Pearson
and W .F .R. Weldon, focused on statistical rigor
and the analysis of continuous, subtle phenotype
variation like height and weight. And they found
Mendel's neat, discrete categories simplistic.
They argued that life was too complex for simple
three -to -one ratios. They thought the Mendelians
were being naive. It was a fierce academic battle.
One side had a clean, simple mechanism, and the
other side had superior statistical methods for
analyzing entire populations. And in a supreme
historical irony, the two warring camps were
ultimately reconciled through the work of R .A.
Fisher. The same statistician who later accused
Mendel of cooking his data. The very same. Starting
around 1918, Fisher mathematically proved that
continuous variation, like height, could be explained
by the cumulative action of multiple Mendelian
factors working together. So both sides were
right. Exactly. And this successful synthesis
of genetics and biometrics led directly to the
modern synthesis of evolutionary biology in the
1930s and 40s, finally integrating Mendelian
genetics with Darwin's natural selection theory
and establishing the framework for biology that
we still use today. Now, before we get to the
modern molecular age, it's worth briefly noting
the tragic rejection of this science in certain
political regimes. Yes. In the mid -20th century,
particularly in the Soviet Union under Stalin
and later in Maoist China, Mendelian genetics
was forcibly rejected. It was outlawed. In favor
of a state -mandated pseudoscience known as Lamarckism
or Lysenkoism. This ideological rejection which
claimed that acquired characteristics could be
inherited and that genetics was a bourgeois science,
led to the imprisonment and execution of real
geneticists. And it resulted in disastrous agricultural
policies that contributed to severe famines in
both nations. It's a stark reminder of the profound
real -world consequences of ignoring established
scientific law for political reasons. Coming
back to the science, though, the final, ultimate
vindication of Mendel's invivible factors is
the modern molecular proof. We know those factors
are genes, stretches of DNA. And the effort to
physically identify and map these specific genes
responsible for the seven traits Mendel studied
that took over a century. It's an incredible
timeline. Mendel laid down the law in the 1860s,
but the scientific world didn't finish the molecular
confirmation until just recently. How recently?
In fact, it was only in 2025 that the last three
of the seven genes responsible for the traits
Mendel observed were finally identified and mapped
within the pea genome. So a complete molecular
map of the seven traits defined by a friar in
his garden was only finished now. That's amazing.
It really is. And looking at the specific molecular
realities just brings his abstract observations
to life. Okay, give us an example. He observed
the wrinkled phenotype, the irregularly shaped
seed. What causes that at a molecular level?
We now know that it's caused by an insertion
of a foreign piece of DNA into the PSSBE1 gene.
And what does that gene do? PSSBE1 codes for
an enzyme called starch -branching enzyme 1.
The insertion inactivates this enzyme. Without
it, the pea plant can't properly convert sugar
into starch, causing the seeds to accumulate
water, shrink when they dry, and thus wrinkle.
So Mendel was measuring the macroscopic result
of a single molecular insertional mutation. Precisely.
And the yellow seed color he tracked so closely,
the dominant one, that's caused by a mutation
in the PSSGR gene. That's GR. PSSGR stands for
state green. It's a gene that typically breaks
down chlorophyll to reveal the yellow pigments
underneath. If that gene is mutated and fails,
as happens in the dominant yellow pea, the chlorophyll
degradation is inhibited and the yellow color
is exposed. What about flower color? The white
flower phenotype, a classic recessive trait,
is caused by a large deletion in the PSBHLH gene.
This gene is necessary for producing the purple
pigment, anthocyanin. No gene, no purple, so
the flowers are white. And even plant height,
which he described as either tall or dwarf. That's
caused by the PSGA3OX1 gene. This gene is crucial
for synthesizing the plant growth hormone jabrilin.
The dwarf plants, the recessives, have a mutation
that stops the hormone production so they don't
grow tall. These molecular discoveries just validate
with absolute certainty that his quantitative
model was mapping real physical biological entities.
After this incredible journey, what happened
to the man who gave us this blueprint? Mendel
died in 1884, still embroiled in those tax disputes.
And in a final tragic irony related to those
disputes, the succeeding Abbott, worried about
potential governmental scrutiny and intervention,
burned all of Mendel's personal and scientific
papers. He burned them. He burned them. He wanted
to close the book on the previous administration's
affairs. We lost decades of scientific records,
potentially those very raw data sheets that might
have resolved the statistical paradox once and
for all. But his posthumous legacy is now immense.
In 2021, for his 200th birthday, his body was
exhumed. Right. And scientists analyzed his genome,
revealing that he had a predisposition to heart
problems and confirming his body height at 168
centimeters. And he's commemorated globally now.
There's a Mount Mendel in New Zealand, the Mendel
Polar Station in Antarctica. His time did indeed
come, but only long after he was gone. What a
journey we've charted today. From the financially
struggling gardener whose sister sacrificed her
dowry, through the seven meticulous years in
the garden, to the statistical paradox that still
challenges his integrity, and finally, the ultimate
molecular proof that arrived just a few years
ago. Gregor Mendel's ultimate success really
validates his belief, my time will come. His
work proves the power of systematic mathematical
observation. even when you're operating outside
the scientific establishment. The ultimate knowledge
nugget here, for me, is that incredible juxtaposition
of historical oversight and modern clarity. He
defined his factors, the basic units of life,
in the 1860s with a theory that Darwin missed
completely. Yet it took us until the year 2025,
a century and a half later, to fully identify
the molecular location and mechanism of the seven
simple traits he was tracking. He saw the consequence
long, long before we could ever see the cause.
And that brings us back to that central mystery,
the Mendelian paradox. We discussed the theory
that Mendel, an obscure genius, might have felt
compelled to simplify his data just slightly
to ensure his revolutionary and ultimately correct
theory of inheritance was heard and accepted
by a rigid, skeptical scientific world. It forces
you to consider a really difficult choice. If
your statistical evidence is technically flawed,
but your underlying scientific conclusion is
conceptually true and leads to a revolution in
understanding, what's the right path for an innovator?
Does the quest for acceptance, the moral imperative
of advancing scientific knowledge, sometimes
justify actions that challenge strict scientific
objectivity? That is a deep dive for another
day.