A while ago I had the pleasure of being at home when some Jehovah’s Witnesses came by. After talking to them I realized to my horror that they understood evolution to mean that a chimpanzee gave birth to a fully formed modern man. I’ll probably never see them again but I’ve been wrapping my head around an easy explanation of what evolution actually is ever since and this is my attempt at an easily understandable explanation.
The simplest example I can think of is photographs. I think I have heard this comparison somewhere, but cannot for the life of me think of where. In any case; evolution is kind of like if you take a portrait photograph of a person every day from when she is born to when she dies except that every photograph represents a generation of creatures. Every generation is recognizably similar to the one before it and the one after it and yet slightly, very subtly different from both. At some points the differences between generations are bigger and change happens faster. And still, at some more or less arbitrary point we assign one generation as well as the ones after it the status of a new species just as we as a society assign, at some more or less arbitrary point, the status of a child, a teenager, an adult, a senior citizen.
Evolution, then, is not so much about individuals as it is about generations. Individuals matter, of course, but not as much as populations. The rate of mutation is generally pretty high but some 90+% of all mutations are neutral with the rest divided into beneficial and detrimental mutations. The individuals with detrimental mutations tend to die out fast, without leaving progeny, whereas the beneficial mutations spread in subsequent generations.
Mutations, though, are not the primary method of speciation for sexually reproducing life forms. Sexual reproduction uses the genetic code of two individuals to form one individual, causing that one individual to be different from both its parents even without mutations. Even siblings from the same parents vary. This then, is what forms the basis of evolution by sexual reproduction; the natural variation between individuals.
Something that always irks me is the way that nature shows present evolution as the defining moment when the cheetah catches the antilope or when she doesn’t and her cubs die of starvation. Sure, it’s that. But it’s not only that. Evolution also shows in the way that meerkats post sentries to look out for predators, in the way that buffalo form a circle around their young to protect them as well as in the way that we humans care for our weaker brethren. Evolution is survival of the fittest. But fitness in the context of evolution is not only physical fitness. We humans are absolutely useless against predators. We’re releatively small if you compare us to the bison or moose that packs of wolves routinely take down. Our teeth and claws are pathetic and we have no natural armor. And yet we are at the very top of apex predators. Intelligence plays a part, but a lone human – however intelligent – stands very little chance against everything that wants to kill us on this planet. We are social animals and evolution has made us so, giving us an advantage that forms the basis of our place on the top of the food chain.
For me, possibly the coolest thing about evolution is that even when creatures evolve into new species, they maintain their ancestral lineage and everything that entails. That means that if a pegasus ever presented anywhere, evolution would immediately go bunk. It also means that we homo sapiens are still apes, mammals, chordates and animals. And just as we are all those things, the creature on the right is what a dinosaur looks like today.