In 1859, in Apocalypse biblical proportions
occurred in the Western Hemisphere. This was not the kind of apocalypse you might
imagine. Nothing physical was destroyed. But the destruction of conventional,
intellectual, social, and religious thinking was equally apocalyptic. So what
happened in 1859? A book called "On the Origin of Species by means of natural
selection" was published, by a little known person by the name of Charles Darwin. And
the world has never been quite the same. We don't realize today how this impacted
Society of the time, but suffice it to say that 160 years later, we are still
affected by it. Charles Darwin changed the way people look at living things.
Most Western society at the time had believed the biblical account of
creation, before this intellectual earthquake. Today evolution is one of the
most tested, well established theories backed by solid evidence, in all of
science. Yet it remains one of the most misunderstood. Here're some common
statements that you will hear. "Evolution makes organisms change to better suit
their environment." "Evolution occurs by random chance and mutations." "Humans are
the most evolved species." Evolution is just a theory, so it's speculation." If
humans came from monkeys, there wouldn't be any more monkeys." Thermodynamics
disproves evolution." Why are all these statements incorrect? How does evolution
actually work? And why do so many people get it wrong? This is one of the most
important topics in all of science in my opinion. And that's coming up right now...
First let's define evolution. Evolution is inherited change in a population of
organisms, over time, resulting in appearance of new forms, under the
influence of pressure from the environment. The first thing to note is
that changes are in populations, not individual organisms. So for example, if
an elephant finds itself living in a very cold climate for a very long time,
it will not become hairy, like the extinct woolly mammoth, in its lifetime.
But over successive generations, the environmental pressure will likely cause
hairier versions of the same breed of elephant to have a survival and
reproductive advantage. So subsequent generations will likely get hairier,
because those hairier elephants in the population are likely to have more
opportunity to reproduce. Their offspring will have inherited the hairy trait. The
change would occur in the population over time, not the individual, and not
suddenly. Another point to note is that this change does not occur by random
chance. Mutations are caused by mistakes that happen when a cell makes a copy of
its genetic information, during the cell division process. Mutations are random,
but they are driven by a non-random process called natural selection. Natural
selection is the opposite of random chance. It's driven by a survival and
reproductive advantage. And these changes in populations are not typically caused
by sudden beneficial random mutations either. Mutations do provide a
critical source of variation in the gene pool of large populations. But the vast
majority of these genetic mistakes, called mutations, are either neutral or
harmful. It is estimated that only about 0.01% are beneficial, meaning
99.99% of all mutations are neutral or harmful. But even the small amount of
just 0.01% is enough to be a significant driver of
evolution, because it generates the genetic variation on which natural
selection can act. Any variation that makes
organism more fit for survival is more likely to spread in the gene pool
through this process. But this idea of "fitness" does not mean that the strongest
survive. A better fit organism does not mean that bigger, faster, more ruthless,
smarter, or stronger individuals are favored. Only individuals that have a
better chance for survival and reproduction are favored. Strength, size
ruthlessness, or intellect does not equal more fit. Ultimately, evolution is not
goal-oriented or a linear process towards some kind of "progress." It is
simply about fitting best in one's environment, and having the opportunity
to reproduce. Some organisms may not change over long periods of time. Take
the example of the American alligator. The fossil record indicates that it has
stayed largely the same for 8 million years. If there are no major changes in
the environmental conditions, and if a species is already well suited for life
in those conditions, why would it change? Also the idea that humans are the most
evolved species because we are cleverer, or faster, or have more nuclear bombs,
than any other species is plain wrong. If you think you're superior to a tuna, try
living underwater for 40 years. Humans are not the most successful species on
the planet. Our planet is dominated by single-celled organisms there are 10^30
single celled organisms weighing 10^14 kilograms. The weight of all
humans is 10^11 kilograms. If you go by weight, then even insects are more
successful than us, weighing 300 times more than all humans combined. What about
the idea that evolution is only a theory, that it's about faith and not evidence?
First, in science, a theory is not simply a hypothesis, meaning a speculative and
unprovable idea. In science, theories are well supported explanations. A theory
means that it is a model capable of being tested by experiment or
observation, and able to predict future observations of the same kind. It's based
on a careful and rational examination of the facts. Calling
something a "theory" is a good thing not a bad thing in science. So if someone says
that evolution is only a theory, ask them if they know what a scientific theory
actually is? It's still called a theory because it's still subject to
examination and confirmation. We have the theory of relativity, and the theory of
gravity too, which are also very robust theories. One distinction should be made
here when people say that evolution cannot explain how life started. That is
absolutely correct. But that's not the purpose of the theory of evolution.
Evolution only works on populations of living organisms. How life first started
is called abiogenesis. And it is not well understood yet, like evolution is. I made
a video about it if you want to know more about it. Then there's the statement,
"if we evolved from monkeys, why are there still monkeys?" First, we did not evolve
from monkeys. We didn't even evolve from chimpanzees or gorillas. Rather, evolution
shows that we share a common ancestor that lived probably around ten million
years ago. This ancestor was not a chimpanzee or gorilla but just a common
ancestor of all modern apes, including us! Go back further, about 25 million years
ago, and this common ancestor of ours, shared a common ancestor with modern
monkeys that live in Africa and Asia today. So that 25 million year old
ancestor is our ancestor too. In fact, if you go back far enough, all living things
on earth have a common ancestor. We're even related to all plants, mushrooms, and
bacteria. Now we get to the commonly held idea that the laws of thermodynamics,
namely entropy, disprove evolution. the idea here is that evolution cannot be
correct because it defies a fundamental law of physics, that entropy or disorder
increases over time, whereas complex life appears to be a drive towards more and
more order. Astronomer Chandra Wickramasinghe famously told a court in 1981, "the
chances that life just occurred are about as unlikely as a typhoon blowing
through a junkyard and ding a Boeing 747." This proves that even
highly intelligent science educated people can totally misunderstand and
mischaracterize evolution. A slightly better analogy would be something like
this: Start with a million junkyards. Put a tornado through each. Exhaustively test
the wreckage left after each tornado to find the most flight worthy object. Make
a million exact copies of that flight worthy object and junkyard combination.
Put another million tornadoes through it. Run exhaustive tests to determine the
most flight worthy object. Make a million more copies of the junkyard and flight
worthy object. And keep doing this over and over, millions of times until you
produce some kind of machine that can fly. It could be very simple and crude. Then
make millions of copies of that, and further refine for flight worthiness. And
keep doing this over and over for millions of years. You will end up with
something that might be even more flight worthy than a Boeing 747...
if the evolutionary driver is flight worthiness. If you pick even the simplest
bacterial life today and calculate the odds of getting their genome by randomly
shuffling DNA sequences, the odds are astronomically small. But random
shuffling is not the way evolution works. The idea of entropy applies to closed
systems. Put crudely, a closed system where matter and energy are conserved,
gets more disorderly over time. The earth is not a closed system.
The Sun is spraying it with huge amounts of energy every day. This energy is
driving the thermodynamics of the earth. Overall entropy is increasing of the
closed system that contains the earth and the Sun. But this does not mean that
pockets of lowering entropy cannot exist. Your refrigerator is a prime example. The
food inside is getting cooler, and it's entropy is decreasing. But if you feel
the vents outside that refrigerator, you'll find that it's heating up your
house. The entropy of your whole house, if it was a closed system, would be
increasing. To understand evolution, you need to appreciate three things. First,
that quadrillion to 1 chances actually happen all the time.
Second, that while mutation is random, which mutations survive is not random.
It is a systematic process that results in adaptations over time, influenced by
environmental factors. And thirdly, given enough time, the accumulation of one
beneficial mutation after another can produce amazingly complex systems.
Although the present-day observational results of evolution can appear to be
impossible, it's a process that given enough time and influenced by selection
and other environmental pressures, can make the impossible extremely likely. For
the past 160 years, scientists have tested this theory every imaginable way -
from field studies, to fossil studies, to computer modeling, with every imaginable
organism. Each new test has only added to the already overwhelming body of
evidence to support this theory. There's not a single piece of credible evidence
to disprove it. There's not really much in science that is as well proven. Famous
French Jesuit priest and philosopher, Pierre de Chardin, said
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