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Comment by alan_cx | Hacker News Reader

This is way, way out of my knowledge, but...

Is the term "Missing link" actually useful? Seems to me that what we keep doing is create more "missing links" with each discovery in the chain. We are sort of filling in gaps created each time we, er, find more missing links. In a 1000 years, we'll still be finding missing links until the whole thing is perfectly mapped out, if that is possible.

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There's the Creationist "missing link", and then there's the one used by sane people. A biological missing link would for example be if we didn't have Archaeopteryx. It's true that this of course creates two new gaps in the evolutionary chain, but those aren't as annoying as the big gap before :-)

It's useful to illustrate the big gap that wasn't covered between some species.

I don't think the analogy with "links in a chain" is good though, but instead "link in the tree diagram".

Tree, yes much better term.

Although as a get out, I would try argue that in my head, even if not conveyed in my post, the the branches are sort of chains... Even then I can see that falling apart.

But yeah, over all, tree is much better.

I'd say the usefulness of the term is to cover cases where, as here, scientists aren't sure how predecessor A evolved into successor B.

Wouldn't that imply lots of missing links? Or are the vast majority of evolutionary, er, jumps known and understood?

My minor point was about a "missing link", in normal conversation it is used as though its one specific fundamental thing. Seems to me there are or would be many missing links.

Or, am I just pedantically reading far too much in to something that is a lose term and not a specific scientific thing? And now I think about it.....

There are usually lots of missing links in a chain, so to speak, but a "missing link" typically means any (reasonably estimated to be) definitive ancestor of Species 1,2,3...N, where 1,2,3...N are believed to be descended from a common lineage, but there is no extant proof of such. Even if there are 200 missing ancestral species in a theoretical lineage, a "missing link" is any of those 200 that demonstrates that the lineage existed, and that establishes its directionality. A missing link is a sufficiency, not necessary the completer of a set.

To your point: the word "link" implies that only one piece of a chain is missing, and furthermore, it suggests a linear relationship. It's misleading in both of those cases. But it makes for a good, easily understood metaphor.

Zeno's arrow paradox for evolution? Interesting.

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.

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...

> 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

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