Explaining evolutionary biology I


By Abdulrazak Ibrahim

A few years ago, we had a long discussion around evolution on this street. One of the lessons I came out of that discussion with was that there’s no point trying to convince anyone about the fact of evolution, let alone “debate” it.

And one of the main reasons is the often repeated sentence “evolution is just a theory”.

Really? So you think if something is a theory, it cannot be true?

Anyone who doesn’t understand that theory in science is not the same as theory in other disciplines, probably needs to learn basic science from secondary school first, before attempting to interrogate evolution.

But discussions on evolution remain relevant because new and emerging methods that address many of our problems are premised on evolutionary principles.

A few years ago, Lehgninger’s Principles of Biochemistry (the most commonly used text book in biochemistry worldwide. My favourite actually) barely had a few passages on evolution. Today, every chapter of the book demonstrates the evolutionary underpinnings of the subject under discussion.

This is why Theodosius Dobzhansky, a biologist and Eastern Orthodox Christian said “Nothing in biology makes sense except in the light of evolution”.

I mean think about it. Almost everything we know about human genetics emerged from the study of model animals like fruitflies and even lower organisms like bacteria. And the only reason why many drugs work on humans is because they have first been tested to have worked on laboratory animals.

For me, it is a tragedy that the teaching of science in Africa and Nigeria in particular, is characterized by denial of evolution.

Regrettably, this denial often emanates from educators themselves, even in the face of all the evidence from fossils, molecular biology records and evolutionary history. One needs only to read.

But many biology teachers have stood before their pupils and told them, “look I am going to teach you this thing but don’t take it serious”.

The understanding/appreciation of evolution is the basis for recognizing our place as Homo sapiens in the universe (and in my opinion, that doesn’t have to detach us from our spiritual or religious leanings).

Once you grasp that, you find yourself in a vast and awesome universe that dwarfs the tiny geocentric notions of our ancestors.

Of course it’s not nice to be told that you are only half a chromosome from being a chimpanzee, but the power that comes with that knowledge cannot be measured.

While teaching molecular biology, I often ask students to stand at the entrance of any busy school, hospital, airport or roadside and watch people passing by. I draw their attention to reflect on the undeniable resemblance to every kind of primate; chimpanzee, orangutan, bonobo, etc they see.

This resemblance has been proven at molecular level.

Bone by bone, molecule by molecule, cell by cell, we have been proven to be the result of evolution; primate mammals that descended from a common ancestor along with chimpanzees.

But like some city dwellers, whose village relatives are visiting for the first time, many humans are embarrassed by their resemblance to other primates.

Although they would agree that tiger, cheetah, leopard, lion, cat are related; that many birds are related, that donkey, zebra, horse are related and that lizard, crocodile, alligator are related. But extend the same judgement to humans and chimpanzees? No 😄

Once you get evolution, very few things are mysterious to you.

Needless to say that evolution is not about Darwin or Darwinism (whatever that means) and that it is not a religious belief or dogma.

Evolution explains the change of allele frequency and epigenetic markers in populations over a period of time, leading to radiative speciation.

A critical raw material of evolution is mutation, which is change in the way our DNA is arranged.

With an average reproductive age of 25 years, the average number of mutations that accumulate between a human parent and its child is 36. This means between a child and a father, there are 36 mutations partly accounting for the differences between them.

Between that child and its grandparent, there are 72. Between the child and its great grandparents, 108.

With every accumulated set of mutations, phenotypic changes are clearly visible.

As you work your back into this historical mutation, you’ll reach a great great great great grandparent that doesn’t appear to phenotypically have anything with the child.

Biologists have travelled as far as 7.5 million years back in this direction and made the startling and uncomfortable discovery of an ancestor that cannot be said to be human by any definition.

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