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Comment by xophe | Hacker News Reader

Also out of my knowledge, but the hypothesized tree of evolution contains only distinct species AFAIK. A true missing link would be an intermediate stage, like catching the first fish with legs as it adapts to land. Fish with wings aren't interesting because they are an (extant) species in their own right.

It's like catching someone on a layover -- you're very clearly in the middle of two stable (but distinct) spots. But you don't spend much time there -- which is why it's been so tough to find.

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> Also out of my knowledge, but the hypothesized tree of evolution contains only distinct species AFAIK. A true missing link would be an intermediate stage ...

They're all species. There's no such thing as an intermediate non-species. Species are conventionally defined as a group that breeds with its own group, and are distinguished by the fact that they cannot breed with other species. So all those intermediate stages were also species.

Some species didn't last very long, and the farther back in time we go, the less chance we have of locating clear evidence for particular species. But that doesn't mean they weren't species, as that term is defined.

There is no difference between "distinct" or "transitional" species. All species are transitional, that's the way evolution works. Some species are more long lived than others due to being well fit to their ecological niche but every species has the potential to evolve to other species even so.

One might consider as "transitional" those species that exist between stages of punctuated equilibrium (if you consider punctuated equilibrium valid).

It's not hypothesized, it's theorized. There's a massive difference between the two scientifically.

Fish with legs can be found in some pet stores. https://en.wikipedia.org/wiki/Lungfish

Also inb4 Futurama fans start complaining about the endless "chain" of evolution. It's not that simple -- similarity does not imply inheritance.

Here's the screenshot from that episode:

http://pool.theinfosphere.org/images/5/57/Human_Evolution.pn...

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