View Full Version : Evolution question
02-08-2001, 10:02 AM
Has any creature ever evolved twice? I don't mean the exact same creature of course since that would be impossible, but have two creatures with extremely similar characteristics ever evolved in different parts of the world independently of one another?
02-08-2001, 10:11 AM
Marsupial lions in Australia: http://www.jps.net/sabado/thylacoleo.html
Plenty of single characteristics have evolved several times, e.g. flight & eyes
02-08-2001, 10:12 AM
bats and birds
emu's and ostriches
fish and whales/dolphins
What is your definition of "similar?"
02-08-2001, 10:48 AM
Zillions of examples. How close do you want 'em?
True moles, Australian marsupial moles, African golden moles.
True anteaters, marsupial anteater (Numbat), Aardvark.
Sabertooth cats (extinct), South American marsupial sabertooth (extinct).
Horses, South American notungulate "horses" (extinct).
Birds: many examples, e.g. New World Vultures (related to storks), Old World Vultures (related to eagles).
There is an African bird called the longclaw that is extremely similar to the North American meadowlarks, right down to the plumage pattern - a layman would be hard put to distinguish them, even though they are completely unrelated.
02-08-2001, 10:56 AM
Buzzards and vultures. Sometimes, certain lifestyles (in this case, circling for hours in the air looking for dead stuff--hence the large wingspan--then sticking your head inside a dead animal carcass and not having feathers get stuck--hence the bald head) results in convergent evolution. I don't have a cite, but I believe many woodpeckers are a result of convergent evolution. A long, pointy beak is just the best thing for getting at insects inside tree bark.
02-08-2001, 11:29 AM
The longclaw/meadowlark example was the kind of thing I was asking about. I was just envisioning travelling to another place, seeing (for example) a frog and saying "hey! We have those back home!" but then finding out that this frog is as related to the frog from your home as a cow is to a beaver.
02-08-2001, 11:36 AM
Wolves, Thylacine ("Tasmanian Wolf")
Wolverine, Tasmanian Devil
Hyaena, Osteoborus (Extinct american bone-crushing dog)
Hippopotamus, Toxodon (S American notungulate)
Rhinoceros, Arsinotherium (African Two-horned critter)
Carnivores, Creodonts, and all sorts of small marsupials
Dolphins, Sharks, Ichythosaurs
Flying Squirrel, Sugar Glider, Flying Lemur
Snakes, legless lizards
Dozens of phyla of different reef-building filter feeders
Baleen Whales, Basking Shark
Colibri: Thank you for bringing up my beloved Thylacosmilus!
And let's add to the list of Moles, Golden Moles, and Marsupial Moles the lovely and enchanting Pink Fairy Armadillo, Chlamyphorus truncatus!
02-08-2001, 11:40 AM
While I have no details, the ancestors of the Whales -- the Meonyschids (sp?) --are often called "wolf-like" except that they had miniature hooves on each toe!
02-08-2001, 07:56 PM
The word that would help your search is "convergence". For individual features of organisms look up "homology".
02-09-2001, 10:44 AM
If you don't demand identical plumage (and many of these are "little brown jobs" anyway), both South America and Australia have lots of "wrens," "flycatchers," "thrushes," "creepers," "nuthatches," "thrashers," etc, etc, that are unrelated to their Northern Hemisphere counterparts. The South American ones have internal anatomical features that allowed ornithologists to classify them in different families, but until about 15 years ago many of the Australian forms were classified with unrelated Eurasian groups, until genetic analysis showed they were entirely distinct.
Among nectar-feeding birds, the Sunbirds, smaller Australian Honeyeaters, Madagascar Sunbird-Asitys, Hawaiian Honeycreepers, and neotropical Honeycreepers (related to tanagers) all look and act very similarly (and although they differ in plumage, most tend to be very colorful) and would be classified by a layman as being the same kind of bird, even though they are indenpendently evolved and differ anatomically.
And even an ornithologist would have trouble telling a true quail from a button-quail (related to rails) in the field, without identifying it to species-level.
02-10-2001, 04:44 AM
I think one of the things that made the lightbulb go on in Charles Darwin's head (he was so smart that he was seeing lightbulbs long before Edison) was that birds in different locations that fill similar ecological niches often have similar adaptations (beak shape, etc.) even though they obviously aren't closely related. All the birds on Island A might be apparently closely related to one another, while birds on Island B are more closely related to one another than they are to the birds on Island A, but all the walnut-eating birds on Island A and the walnut-eating birds on Island B will have certain adaptations in common. What Colibri said, in other words. I've also heard about this kind of thing happening with fish in isolated lakes.
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