Biology / Evolution / Genetics / Science

Why chimpanzees are still around

“If humans evolved from chimpanzees, why are chimpanzees still around?”

Further to the last post, okay, I’ll bite. Here is an explanation of how chimpanzees are still around even though the theory of evolution is true.

There’s one really simple way to say this, which has its own weaknesses. Try this question: “If you come from your parents, why are your parents still around?” It’s really the same question, in a way. It is totally possible for a new species to form by splitting off from an existing species which remains the same, because it only requires that offspring different to the parent be born. As an example, consider the case of Biston betularia, the peppered moth.

In industrial parts of the country, lichen died off the trees and the trees were blackened by soot, making the original form of Biston betularia really conspicuous. This is a disadvantage, and the original light form (often called a “morph”) of the peppered moth died off in these areas because it was easy for predators to spot. However, peppered moths which happened to have a mutation giving them a dark pigmentation, a melanic morph, were camouflaged against the blackened trees and survived really well to breed. Had this situation kept up, you could have had a new species of peppered moth in those areas, while the original pale morph survived in non-industrial areas.

It’s really that simple: evolution doesn’t consume existing species. If that were the case, you could easily disprove evolution by pointing out that after a mass extinction, the number of different species in the world should fall. Needless to say, the fossil record doesn’t support that. But evolution doesn’t necessitate one species simply becoming another species; one, two or many new species can be formed from an original species.

The other problem with the question of why chimpanzees are still around is that… we didn’t evolve from chimpanzees. Rather, humans and chimpanzees evolved from the same common ancestor — just as you and your cousin share a grandmother, chimpanzees and humans share an ancestral species. Say your surname is Evans and your cousin’s surname is Jones. That doesn’t mean you aren’t related, but it’s a way of modelling different species. Grandma Evans had a son, John Evans, and a daughter, Sioned Evans. Sioned Evans married Jack Jones and became Sioned Jones, giving birth to children with the Jones surname, while John Evans married Margaret Smith, who became Margaret Evans and gave birth to children with the surname Evans (including you). You’re an Evans, and your cousin is a Jones, but you are both still related to Granny Evans.

Family tree demonstrating analogy between human familial relationships and evolutionary relationships

In the same way, some descendants of the ape ancestor became chimpanzees, and some became humans. That’s a really simplistic view of it, but it helps to remember that chimpanzees and humans are more like cousin species than parent and child species. We adapted to different environments, and so our physical forms changed. That ancestor may or may not still survive in a similar form today: it’s possible that there are three sets of offspring lineages: chimpanzees, humans, and one more like that ancestor. It’s possible that that line has died out by now, or given rise later to different species.

The point is, species don’t have to die to give rise to new species. That’s why it’s completely bananas to claim that the existence of chimpanzees proves evolution isn’t real — it’s like saying that your existence means your cousin can’t exist.


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