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Crabs evolved at least five times from separate groups of crustaceans (2021)

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Re: Crabs evolved at least five times from separate groups of crustaceans (2021)

#81

Post by astrange »

jleyank wrote: post #45
astrange wrote: post #33

Earlier quoted context omitted.

This reminds me of ESR's Jargon File, which kept defining "hackers" as liking or doing things when it was actually just him.

I forget it’s history, but the jargon file predates esr. Check levy’s heroes of the computer revolution about the original mit hackers.

I wasn't talking about the innocent previous authors in my post where I specifically complain about ESR!

Wow, that was a while ago though.

https://news.slashdot.org/story/03/06/08/1534249/esr-recasts...

Re: Crabs evolved at least five times from separate groups of crustaceans (2021)

#82

Post by Retric »

me_me_mu_mu wrote: post #78
version_five wrote: post #21

Earlier quoted context omitted.

There was a recent article on here about how species that looked alike were not necessarily related and is was more common to have physically dissimilar but geographically close species that were evolutionary relatives. One of the points was that convergent evolution was more common than people thought. These stories appear to support the convergent evolution assertion

Curious if that applies to humans as well. I’m from S Asia and well.. I do have my distinct looks that I share with my family and community, that are different from other communities. Are humans like that as well? I am aware of the migration theories and people crossing ice bridges and all that, but did people evolve in different areas and then spread out after settling their original area?

The closest example of convergent evolution in humans would probably be native populations in South America redeveloping darker skin tones to deal with sun burn the same way we initially had it in Africa. I don’t know the exact genetics, but it seems to be an independent adaptation rather than a holdover from an older population.

There might be some others such as lactose tolerance that are less obvious.

Re: Crabs evolved at least five times from separate groups of crustaceans (2021)

#83

Post by goodcanadian »

me_me_mu_mu wrote: post #78
version_five wrote: post #21

Earlier quoted context omitted.

There was a recent article on here about how species that looked alike were not necessarily related and is was more common to have physically dissimilar but geographically close species that were evolutionary relatives. One of the points was that convergent evolution was more common than people thought. These stories appear to support the convergent evolution assertion

Curious if that applies to humans as well. I’m from S Asia and well.. I do have my distinct looks that I share with my family and community, that are different from other communities. Are humans like that as well? I am aware of the migration theories and people crossing ice bridges and all that, but did people evolve in different areas and then spread out after settling their original area?

From genetic studies, we can safely say that all humans are closely related and members of the same species. We are not an example of convergent evolution.

Re: Crabs evolved at least five times from separate groups of crustaceans (2021)

#84

Post by kaelspencer »

irrational wrote: post #51
vimy wrote: post #47

Earlier quoted context omitted.

Not exactly what you’re asking but whales used to be land mammals. > It is believed that modern-day whales evolved from land-based animals about 55 million years ago. These land-based mammals are believed to be hoofed mammals, sharing a common ancestry with even-toed ungulates such as the cow and the deer. > Evolution of Whales Whales started their journey as all other organisms have, as single-celled bacteria. An ev…

Which one of these was also the common ancestor of the hippopotamus?

I'd like to suggest OneZoom for exploring these relationships.

http://www.onezoom.org/life/@Hippopotamidae=510764?img=best_...

Re: Crabs evolved at least five times from separate groups of crustaceans (2021)

#85

Post by andrewflnr »

Retric wrote: post #82
me_me_mu_mu wrote: post #78

Earlier quoted context omitted.

Curious if that applies to humans as well. I’m from S Asia and well.. I do have my distinct looks that I share with my family and community, that are different from other communities. Are humans like that as well? I am aware of the migration theories and people crossing ice bridges and all that, but did people evolve in different areas and then spread out after settling their original area?

The closest example of convergent evolution in humans would probably be native populations in South America redeveloping darker skin tones to deal with sun burn the same way we initially had it in Africa. I don’t know the exact genetics, but it seems to be an independent adaptation rather than a holdover from an older population. There might be some others such as lactose tolerance that are less obvious.

I'd be very interested in hearing about that. My guess would have been that it was more a matter of the previously suppressed genes for dark skin coming back to the fore.

Re: Crabs evolved at least five times from separate groups of crustaceans (2021)

#86

Post by crooked-v »

ativzzz wrote: post #63
mirekrusin wrote: post #61

Earlier quoted context omitted.

I wasn't aware of that some time ago, it's a fascinating insight. I got a lightbulb (going wtf/dark actually!) when watching cartoon or something with triceratops. They looked so much like rhinos. But had eggs. I had trouble reconciling it with evolution. They were so far ancestor-wise but so close physically-looking wise. Convergent evolution is very interesting. It suggests aliens may not be that different from us…

> It suggests aliens may not be that different from us after all, if exist. Alternatively, they are the more evolutionally convergent species and we will evolve towards something inhuman

This has me thinking of some surrealistic scifi with a Space Crab Parliament that only allows species that have sufficiently carcinized so as to be indistinguishable from the existing members.

Re: Crabs evolved at least five times from separate groups of crustaceans (2021)

#87

Post by andrewflnr »

samatman wrote: post #15

Even more wild to me is that saber-toothed cat-like predators evolved seven separate times: https://en.wikipedia.org/wiki/Saber-toothed_predator

This is especially weird for me since I still don't understand what advantage they provide. It doesn't look like you can really use them for biting, can you? So do you just use them like a grappling hook fixed to your face? I've never seen a convincing answer.

Re: Crabs evolved at least five times from separate groups of crustaceans (2021)

#88

Post by fbarred »

andrewflnr wrote: post #87
samatman wrote: post #15

Even more wild to me is that saber-toothed cat-like predators evolved seven separate times: https://en.wikipedia.org/wiki/Saber-toothed_predator

This is especially weird for me since I still don't understand what advantage they provide. It doesn't look like you can really use them for biting, can you? So do you just use them like a grappling hook fixed to your face? I've never seen a convincing answer.

Wikipedia has a few convincing hypothesis. One is that sabre teeth are important for biting deep and reaching vital organs on large prey. After the megafauna went extinct, so did saber-toothed animals, and this adaptation was no longer needed.

Re: Crabs evolved at least five times from separate groups of crustaceans (2021)

#89

Post by fbarred »

throwaway742 wrote: post #70
gibolt wrote: post #17

Earlier quoted context omitted.

The teeth are already there. A few gradually longer ones makes obvious sense to be a better predator, giving them an evolutionary advantage.

Then why aren't they still around? Why don't they evolve again?

The large teeth may have been useful to hit vital organs on large prey that used to be common but now extinct. No large prey - no sabre teeth needed.

Re: Crabs evolved at least five times from separate groups of crustaceans (2021)

#90

Post by samus »

docmechanic wrote: post #31
AlbertCory wrote: post #16

> We know the process has occurred multiple times and our current grant is aimed at better understanding the drivers and implications What can they actually discover? 10 legs good? But how about 12? [1] > The crab with the longest legs is the Japanese spider crab. It’s not related to spiders, despite its name. When extended, its legs can be as long as 12 feet. Now there's a nightmare for you. [1] https://www.referenc…

If the habitat was the bottleneck, we could learn about a convergence point that tells us about possible non-Earth life. "Whatever the advantages are, they do not apply in all habitats because some groups have also lost carcinization; one modern example being the frog crab."

Fun fact: life has terraformed the Earth (pun fully intended) into what it is today:

- Photosynthesis created and maintains the current composition of the athmosphere. By removing too much CO2, it likely also contributed to several ice ages.

- Early life sequestered almost all the iron in the primordial Earth's sea into sediments, which turned into iron ores.

- We take the presence of such a basic thing as soil for almost granted, yet soil is created and maintained by life itself. At the same time, soil is only absent in environments where only extremophiles can survive. From this follows that it must have taken a lot of time for life to conquer the land and make it hospitable by creating a soil covering.

From these things, I (perhaps hastily) conclude that planets with life could actually look a lot like Earth. Or they can at least be recognized by the presence of chemically and physically unlikely features such as reactive elements like oxygen in their athmospheres.

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