The reason is that the universe contains many environmental niches that are essentially duplicates of each other, leading to convergent evolution. For example Earth contains lots of species that are similar to each other, and within each species there’s huge amounts of redundancy.
There’s often a deceptive amount of difference, some of it very fundamental, hiding inside those convergent similarities, and that’s because “convergent evolution” is in the eye of the beholder, and mostly restricted to surface-level analogies between some basic functions.
Consider pangolins and echidnas. Pretty much the same, right? Oh sure, one’s built on a placental framework and the other a monotreme one, but they’ve developed the same basic tools: long tongues, powerful digging claws, keratenous spines/sharp plates… not much scope for variance there, at least not of a sort that’d interest a lay person, surely.
Well, actually they’re quite different. It’s not just that echidnas lay eggs and pangolins birth live young, or that pangolins tend to climb trees and echidnas tend to burrow. Echidnas have more going on upstairs, so to speak—their brains are about 50% neocortex (compare 30% for a human) and they are notoriously clever. Among people who work with wild populations they’re known for being basically impossible to trap, even when appropriate bait can be set up. In at least one case a researcher who’d captured several (you essentially have to grab them when you find them) left them in a cage they couldn’t dig out of, only to find in the morning they’d stacked up their water dishes and climbed out the top. There is evidence that they communicate infrasonically in a manner similar to elephants, and they are known to be sensitive to electricity.
My point here isn’t “Echidnas are awesome!”, my point is that the richness of behavior and intelligence that they display is not mirrored in pangolins, who share the same niche and many convergent adaptations. To a person with no more than a passing familiarity, they’d be hard to distinguish on a functional level since their most obvious, surface-visible traits are very similar and the differences seem minor. If you get an in-depth look at them, they’re quite different, and the significance of those “convergent” traits diminishes in the face of much more salient differences between the two groups of animals.
Short version: superficial similarities are very often only that, especially in the world of biology. Often they do have some inferential value, but there are limits on that.
There’s often a deceptive amount of difference, some of it very fundamental, hiding inside those convergent similarities, and that’s because “convergent evolution” is in the eye of the beholder, and mostly restricted to surface-level analogies between some basic functions.
Consider pangolins and echidnas. Pretty much the same, right? Oh sure, one’s built on a placental framework and the other a monotreme one, but they’ve developed the same basic tools: long tongues, powerful digging claws, keratenous spines/sharp plates… not much scope for variance there, at least not of a sort that’d interest a lay person, surely.
Well, actually they’re quite different. It’s not just that echidnas lay eggs and pangolins birth live young, or that pangolins tend to climb trees and echidnas tend to burrow. Echidnas have more going on upstairs, so to speak—their brains are about 50% neocortex (compare 30% for a human) and they are notoriously clever. Among people who work with wild populations they’re known for being basically impossible to trap, even when appropriate bait can be set up. In at least one case a researcher who’d captured several (you essentially have to grab them when you find them) left them in a cage they couldn’t dig out of, only to find in the morning they’d stacked up their water dishes and climbed out the top. There is evidence that they communicate infrasonically in a manner similar to elephants, and they are known to be sensitive to electricity.
My point here isn’t “Echidnas are awesome!”, my point is that the richness of behavior and intelligence that they display is not mirrored in pangolins, who share the same niche and many convergent adaptations. To a person with no more than a passing familiarity, they’d be hard to distinguish on a functional level since their most obvious, surface-visible traits are very similar and the differences seem minor. If you get an in-depth look at them, they’re quite different, and the significance of those “convergent” traits diminishes in the face of much more salient differences between the two groups of animals.
Short version: superficial similarities are very often only that, especially in the world of biology. Often they do have some inferential value, but there are limits on that.