The thing about evolution - an animal that takes advantage of an opportunity to live, eat, and breed with survive more often. Extra bits “cost” a lot in terms of food and survival. The cheetah or wolf, for example, does not need a huge brain. Once you are fast, you only need enough brainpower to figure out where the prey will zig or zag next, and how to avoid the horns when they corner it. Extra brain power takes a lot of extra food to keep working - it it’s not going to get you fed or laid more often, you will lose during bad times to the small-brained wolf or cheetah who will live on less food. It’s always a trade-off.
This is also why humans have limited muscle power. Muscles takes food to maintain, even at rest. To strong a human, or too big, will be the most vulnerable during famine.
Basically, the result in evolution is the most appropriate compromise - the “Goldilocks” zone, just perfect. If an organism is fairly specialized or exotic, it means they have latched onto a very reliable source of food (at least at one time). Then, like giraffes and the tall trees, they have become more and more specialized over time to better exploit that ecological “niche”.
For a nice example of this, I like this video, where Richard Dawkins talks about the laryngeal nerve. This is a nerve that goes from the brain to the larynx. In some of our early ancestors, it took a pretty direct route, but because of historical accidents, it now takes weird detours around the bodies of large animals (and humans). In a giraffe, it only really needs to go two inches, but instead of hopping right across, it goes all the way down the giraffe’s neck and back up again. It’s just the kind of thing that evolution does that a designer would never do.
No. It’s not. Failing to understand this is behind 90% of the misconceptions I see about evolution. Evolution is NOT random. The biosphere of the earth is NOT the result of eleventy gazillion coin flips all landing heads-up.
Mutations are random; selection is NOT. That’s absolutely critical to understanding how it is that we see what we see. Selection selects. Nonrandomly. That’s why it’s called that. It’s a natural, undirected, purely automatic system that is the result of competition between genetic variants in the environment. That is the driving force. That is what brought us from the primordial soup to chicken noodle soup. And chickens. And the wheat that made the noodles, and the virus that gave you the cold that you’re eating the soup to soothe. There is no goal, there is no direction, but there is, vitally, nonrandom selection.
It would if you were a Platypus. An intelligent Platypus would be sure he was the pinnacle of evolution and the crown of creation.
A hairless, bipedal, terrestrial ape with a hypertrophied brain would seem just as outlandish and unlikely as a Platypus if we weren’t one ourselves.
Most likely it was both, as has been the case whenever a group of H. sapiens met a less advanced group of our own species. But the group ends up extinct except for a few genes still carried in the victorious population.
The element of direction only seems to hold true when the environment has consistent selective pressures. As long as being big is selected for, you expect generation 100 to bigger and generation 10,000 to be bigger still. But at some point, big will no longer be selected for - maybe your bones aren’t strong enough, or you can’t find enough food, etc. Then (again, assuming no change in the selective pressures) a species is likely to settle into an equilibrium in regards to size.
Some species have reached remarkably stable positions. Crocodilians, for example.
On the other hand, you look at something like Darwin’s finches and you see that beak size skews all over the place. You can look at any individual species and see the selective pressures that lead to that particular beak, but if you look at all of the species or look at them over a long-enough time frame, there’s no overall pattern.
Although increasing size is a trend in hominid evolution, with Homo erectus being much larger that Australopithecus, that was of course reversed in the so-called “hobbits” of Flores, Homo floresensis. Likewise some modern human populations are similar in size to Australopithecus.
There is a gigantic random element. Natural selection only acts after the random event. You can only play the cards you were dealt.
“Evolution is random” is a correct enough one-sentence summary of evolution.
That is, I think, a large part of the “looks like directed” part.
Yes, there is an ineliminable random element in evolution, but “Evolution is random,” is very far from being a correct, or even “correct enough” (whatever that means), summary of the theory. It is not just false, it is actively misleading. The belief that it is an adequate summary is indeed what lies behind much of the misunderstanding of evolutionary theory that is out there, and at least a part of the appeal of creationism.
But you don’t even have to reference that species, since the type specimen for *H. ergaster * (the so-called Turkana Boy) would have been larger than your average H. sapiens today. Still, H. erectus was a wide ranging species and local populations probably had a range of sizes depending on the environment they found themselves in. Which is not unlike our own species.
And of course the Australopithecines (a genus, not a species) ranged widely in size themselves, although the versions that seem to have evolved in us* were on the smallish side.
*There is still debate about which exact species of that genus were our ancestors.
Mutations are random and natural selection is non-directed (in the sense that it’s a dumb natural event, no one’s guiding it) and usually very slow (vis a vis a species’ generation time) so that it is unpredictable, that “random” is the right word.
We could go really anal and say the real randomness is non-existant in the non-quantic world and that coin-fliiping and dice-throwing and lottery-number-ball-selection are not REALLY random, because we could analize the initial conjditions and come up with the result.
I something is not intentionally directed and the results cannot even remotely be predicted then it’s real-world random if not scientifically random.
You say “you can only play the cards you were dealt.” but in fact evolution gets dealt millions of hands. True it is not directed, but neither is it random, since only mutations that lead to reproductive success spread.
There are tons of heuristics for search space exploration, such as simulated annealing and of course genetic algorithms, and while you can’t predetermine which local optimum they wind up at, they are definitely not random, and in fact can be compared with truly random heuristics.
Then there’s self-selection - the finches with big strong seed-cracking beaks, or thin pointy insect-eating beaks, who mated with anything but the same would produce a beak likely only half as good at either task and likely to lose in the competition for food (unless each type of food frequently disappeared and the ability to switch was an advantage). By this method one species gradually becomes two specialized species with different characteristics.
It’s not useful to describe it as ‘random’, because it leads to grave misconceptions - and people end up asking “how come it looks so directed?” (or worse).
Evolution looks like it is trying hard to produce fit-for-purpose solutions because those solutions that are not fit for purpose, nature deals with brutally and dispassionately.
On a related note -
I can’t recall if it’s Dawkins or Gould who emphasised that the visual tree metaphor we have for evolution, especially in scientific illustration, which emphasises the successful branches, prunes off the unsuccessful lineages without regard to their lifespan, and is overall arrayed in a distinctly hierarchical fashion (mammals->primates->apes->humans inevitable being the topmost branch) is part of the overall problem of people’s misconception, and a forest, with the survivors just being particularly tall trees is a better metaphor.
I have noticed that the circular rootless dendrogram is becoming increasingly common for lay illustrations too.
