Early in The Greatest Show on Earth: The Evidence for Evolution, Richard Dawkins raises the question of why the idea of evolution took so long to emerge. The basic concept that life forms change as successful ones multiply and unsuccessful ones die off didn’t require any technology to come up with. So why did it emerge so much later than abstract ideas about mathematics, physics, etc?
One explanation he gives – and which I find interesting – is that people were captivated by a Platonic notion of essential forms. Dawkins convincingly uses the example of rabbits to illustrate what he means:
What we call ‘a rabbit’ now is just a kind of snapshot in the development of that organism, between the ancient emergence of chordates and mammals and the emergence of whatever it is the descendant’s of todays rabbits will become. Given enough time, they will surely include creatures that no modern person would put into the category of ‘rabbit.’
Dawkins suggests that the categorical way in which children learn has something to do with why the Platonic view is so intuitively appealing. Presented with the overwhelming complexity of the world, they begin to put this and that into different conceptual boxes. That habit, useful as it is for making do in the world, may have blinded humanity to one of the most powerful explanations to the very nature of our world and the beings in it.
It is, of course, equally true to say that there is no permanent ‘humanness.’ As a species, we are only human temporarily. Over time, we will inevitably change; and if we were separated into groups that strictly did not interbreed, we would eventually become incapable of doing so. Indeed, given the limitation of the speed of light, that may be precisely the rate of any humans who leave our solar system in order to try to colonize planets orbiting other suns.
We can use the notion of “evolution” or “becoming” or “impermanence” precisely because it is another categorical box – that allows us to grasp transience as if it were stability. Even “transience” is itself a stable notion – it means the same today, yesterday, tommorow.
Dawkins describes how all living things are connected by actual living ancestors.
For instance, you can take any rabbit, then recall its mother and the mother of that rabbit. Going far back through time, the line of succession looks less and less like a modern rabbit. At some point in that line is the actual living creature that was the common ancestor to rabbits and anything else (Dawkins uses the example of leopards).
So, you can trace back to the shrew-like animal that was the common ancestor of rabbits and leopards, then start following the line of descent that led to leopards. You could do the same between any two living beings: from ants to cedar trees to the HIV virus.
Any two creatures beside one another in the line are basically the same, but the endpoints are radically different.
It’s odd to think that somewhere, eons ago, there was an actual living thing that produced descendants that ended up as oak trees and human beings.
Interesting. I’ll have to ponder that one further.
“As a species, we are only human temporarily.”
True – but there really is a category of “human”, and this category does have some permanence. If it didn’t have this permanence they species wouldn’t be able to breed with itself, and would fail.
From the perspective of genes, “enduring categories” are a preservation value, and “the transience of categories” is an enhancement value.
If humanity remains one breeding mass for the rest of the duration of the species, we will always remain ‘human’ in the sense of being able to breed with one another.
Even so, we will probably lose the ability to breed with humans as they exist now, and may change to such an extent that a modern-day human would not identify one of its own descendents as human.
“As we trace the ancestry of modern Homo sapiens backwards, there must come a time when the difference from living people is sufficiently great to deserve a different specific name, say Homo ergaster. Yet, every step of the way, individuals were presumably sufficiently similar to their parents and their children to be placed in the same species. Now, go back further, tracing the ancestry of Homo ergaster, and there must come a time when we reach individuals who are sufficiently different from ‘mainstream’ ergaster to deserve a different specific name, say Homo habilis. And now we come to the point of this argument. As we go back further still, at some point we must start to hit individuals sufficiently different from modern Homo sapiens to deserve a different genus name: say Australopithecus. The trouble is ‘sufficiently different from modern Homo sapiens‘ is another matter entirely from ‘sufficiently different from the earliest Homo‘, here designated as Homo habilis. Think about the first specimen of Homo habilis to be born. Her parents were Australopithecus. She belonged to a different genus from her parents? That’s just dopey! Yes it certainly is. But it is not reality that’s at fault, it’s our human insistence on shoving everything into a named category. In reality, there was no such creature as the first specimen of Homo habilis. There was no first specimen of any species or any genus or any class or any phylum. Every creature that has ever been born would have been classified – had there been a zoologist around to do the classifying – as belonging to exactly the same species as its parents.”
Dawkins, Richard. The Greatest Show on Earth. p.195 (hardcover)
Also described in Dawkins’ book is the remarkable science that has been done on Caenorhabditis elegans.
Every single one of the creature’s cells (959 in the adult hermaphrodite; 1031 in the adult male) has been named, and had its lineage traced back to the original single cell of the fertilized egg. Because the worms have invariant cell lineage, each cell in the embryo invariably splits to generate the same cells in the adult.
It’s amazing that the physiology of any creature is so comprehensively understood.
Fossil finds extend human story
By Jonathan Amos
Science reporter, BBC News
An ancient human-like creature that may be a direct ancestor to our species has been described by researchers.
The assessment of the 4.4-million-year-old animal called Ardipithecus ramidus is reported in the journal Science.
Even if it is not on the direct line to us, it offers new insights into how we evolved from the common ancestor we share with chimps, the team says.
Fossils of A. ramidus were first found in Ethiopia in 1992, but it has taken 17 years to assess their significance.
The supreme product of evolution
Since it is only natural to read this chart downwards and to the right…
The winner is Crocodillians. Space Pope, indeed.
The chart on this page is also wonderful.
If humanity remains one breeding mass for the rest of the duration of the species, we will always remain ‘human’ in the sense of being able to breed with one another.”
This is a good point. The permanence of the category of “human” which allows us to persist is not a static permanence – it is a constant changing while remaining “close enough”. As such, I should have said earlier that it is not the static categories but the consistency of the shifting, within some sort of limits, which allow the continuation of the species.
This reminds of me something Nietzsche wrote in the late notebooks: “To stamp Becoming as Becoming, to give it the character of Being, is the highest Will to Power”. By that he means something like – the most powerful means humans have to dominate over the earth is to grasp change as itself something constant and securable, rather than random and unknowable.
Things can be random while also creating consequences that are constant and directional: look at radioactive decay, or evolution. Both arise from randomness, yet can have predictable consequences.
Regading the second chart linked above (the ‘wheel’), it of course commits the same error as those who pretend the distinctions between species are always sharp. The sharp breaks in the tree were never evident at the time.
It’s a bit odd how genetics are a fundamentally digital phenomenon (ACTG), yet the process of speciation looks quite analogue.
I don’t think the analogy with nuclear decay is useful.
“These latest warnings are stark.
They point to statistics that demonstrate that the extinction rates of animal species are much higher than had been predicted only a few years ago.
The worst affected – according to the scientists from the Diversitas group of biodiversity experts – are freshwater species like fish, frogs, turtles and crocodiles.
The scientists warn that these freshwater species are becoming extinct six times faster than their terrestrial and marine cousins.
Some of the group’s experts predict that by 2025 not a single river in China will reach the sea – except during floods.”