This episode of "Undistorted Science" explores human evolution, moving beyond the simplistic "humans evolved from apes" to delve into the modern scientific understanding of evolutionary mechanisms, particularly focusing on the shift from Darwinian natural selection to the "selfish gene" theory for sexually reproducing organisms.
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The Czech Academy of Sciences presents
the educational series UNDISTORTED SCIENCE
Episode 5: HUMAN EVOLUTION
Humans have evolved from apes.
That's a phrase you have probably heard many times in connection with evolution.
But our aim is to look at evolution through the lens of modern science,
and we will also focus on organisms that reproduce sexually, i.e. on us.
Well, that might interest you, right?
Evolutionary biology is the branch of science
concerned with the biological evolution of organisms,
and the mechanisms that apply to it.
Evolutionary biology uses the results of other biological sciences,
from physiology to ecology, to find answers
to general and specific questions of evolution.
Such as who, why or for how much.
An important representative of pre-revolutionary thinking
was the Swedish naturalist and physician Carl Linne.
Pre-evolutionary thinking is based on the idea of the immutability of species.
Linne surmised that the unchanging order of nature is ordained by God,
and that changes of species are thus out of the question.
But even he was a little disturbed by the fact
that some species are created by hybridization.
Proponents of this view would consider the idea that species can change over time
and that humans could have evolved from apes
unacceptable and absolutely ridiculous.
The author of the first important theory of evolution was Jean-Baptiste Lamarck,
who correctly realized that species are mutable
and that one emerges from another.
He also designed a mechanism to develop purposeful properties in organisms.
However, this mechanism, based on the preferential origin
and inheritance of these preferential traits, was flawed.
And it is not practically applied in evolutionary biology today.
The founder of modern evolutionary biology,
and the main author of the two co-authors of the theory of evolution based on natural selection,
was the British naturalist Charles Darwin.
According to him, and to his colleague Alfred Russell Wallace,
natural selection is the main mechanism of species change.
This theory is now known as Darwinism.
According to Darwin, nature favours those that can make better use of environmental resources,
better resist enemy attacks, i.e. parasites and predators,
are more attractive to the opposite sex, and thus leave behind more offspring.
According to Darwin, the present-day species have come into being
through a long process of biological evolution
driven forward by natural selection.
As a result of random mutations, mostly due to errors in copying genes,
individuals with characteristics slightly different from those of their ancestors
have continually appeared within each species.
As mistakes are more likely to make things worse rather than better,
most of these deviations have been disadvantageous for their carriers.
However, a small percentage of mutations have been beneficial.
This has allowed the carriers to survive and to better reproduce,
and thus pass on more copies of their mutated genes to future generations.
Over time, by gradually accumulating advantageous mutations,
organisms have improved their ability to use resources and to escape their enemies.
The tree of life was growing gradually.
Some branches with their species disappeared.
Others, on the other hand, newly emerged and branched out further.
Well, not all branches are the same, right?
You might not know this, but Darwin's theory
hasn't really been valid for a quarter of a century.
Instead, evolutionary biologists use a different theory to explain evolution,
the selfish gene theory.
It assumes that evolution actually works very differently.
Organisms are not its main protagonists; the subtle and invisible genes are.
The selfish gene theory was elaborated by the British scientist Richard Dawkins
in his famous book of the same name, The Selfish Gene.
He wrote it during his convalescence while treating his broken leg.
He showed that Darwin's scenario of the evolution of life is wrong,
more accurately, that it was only valid until the emergence
of the hugely successful branch of sexually reproducing organisms.
For the evolutionary invention of sex
has fundamentally changed the rules of the evolutionary game.
During sex, among other things, genes from two parents get mixed,
and the offspring acquires a unique set of genes, or rather a set of gene variants,
so-called alleles, and therefore a unique combination of properties
that condition each allele.
To a father and a mother who exhibit excellent combinations of traits,
offspring can be born who will exhibit combinations of either extremely disadvantageous
or, on the contrary, very profitable traits.
Thus, in sexually reproducing organisms,
the inheritance of biological fitness is very limited,
therefore biological evolution cannot take place via the mechanism designed by Darwin.
Dawkins built on the work of his colleagues.
They showed that the evolution of sexually reproducing organisms
is not driven by competition between individuals of a species for the number of offspring,
but between individual gene variants
for the number of copies of themselves passed on to the next generation.
So organisms are not the main protagonists in evolution,
but rather individual variants of the genes
that have created their own organisms - us, in fact.
So the organisms are just puppets which their creators, alleles, subsequently control.
According to the old theory, in evolution, an allele that will program the individual
to produce the maximum number of offspring in their lifetime should win.
But according to the selfish gene theory,
the winner is an allele that will program the individual
so that it can be passed on to the next generation in as many copies as possible.
Most alleles achieve their goal by programming individuals to reproduce as much as possible.
However, some alleles program the individual to help their relatives,
who often carry copies of the same allele, to reproduce.
Still others, to harm their non-relatives.
Individual variants of a particular gene, alleles,
mostly exercise power over their organism indirectly.
They usually influence its creation,
including the brain in animals, but they no longer interfere much with their behaviour
and leave the control to the individual's nervous system.
So actually, we can do whatever we want.
The organisms, or puppets, are sort of allele growers.
However, these alleles have left them with free will in many ways,
and with the ability to change their behaviour based on experience, i.e. the ability to learn.
For some species, like ours, the role of learning and free will is so strong
that we can rebel against the interests of our creators and not reproduce.
We may even sacrifice our own lives for others or for our ideals.
Of course, such behaviour is unlikely to become the norm.
Because the alleles that have produced such an individual
will be transmitted to the next generation in fewer copies or even not at all.
A society in which such unsuccessful alleles occur at least in small numbers, however,
may be more successful in the long run than a society in which there are no such alleles.
There just aren't that many of us that are like this.
The fact that alleles have given us brains and free will was pretty smart of them,
as the properties that may have been advantageous
in terms of the propagation of organisms into future generations
may become disadvantageous in other conditions.
For example, alleles have programmed us in the past to make us like sweet and fatty foods.
This may have been advantageous for our ancient ancestors
who were in danger of starving in winter.
Today, the same characteristics are likely to lead to obesity and diabetes,
therefore reducing the number and quality of our offspring.
The brain, a brilliant evolutionary invention,
allows us to change these eating habits in an instant
when we realize that we are getting fat and we are getting unattractive.
Or even sexual behaviour.
When we find out that an AIDS pandemic has emerged, for example.
As far as matters relating to reproduction,
I mean, who we fall in love with, who or what turns us on sexually,
alleles have left humans in charge of the subconscious.
That is, evolutionarily older parts of the brain.
And so we can't control these things so easily.
Sometimes it's a shame, sometimes, thank God.
Therefore, reason has been left with a rather difficult task.
In hindsight, to justify our choices and behaviour.
A difficult task.
But that doesn't mean that it is more profitable for us to put aside reason
and to follow only the subconscious in reproduction.
We must not forget that the happiness of us puppets has never mattered to the alleles.
Only when our satisfaction has been in line with their own interest,
i.e. in passing on as many copies as possible to the next generation.
In conclusion, let me borrow a few classic words:
be fruitful and multiply as your genes dictate, but don't forget to think.
English subtitles: Studio Beey, 2022
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