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Author
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Topic: A Couple Explanations Please
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Wolf
Inactive Member
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Message 1 of 29 (230920)
08-08-2005 9:57 AM
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As you may already know, I do believe evolution has occurred; however as of right now there are two questions that are eating at me. If we split from a common ancestor with chimpanzees approximately 5 MYA, how is it we have changed so much and chimpanzee's have not. If I understand it correctly Lucy was the first hominid species that was able to walk upright, but looked very much like a chimpanzee. Why such the drastic change in one and not the other? So called "Living Fossils" is my next hiccup. A small list below: Coelacanth Nautilus Sturgeon Tuatara Wollemi Pine Triops Army Ants Cockroaches Bathynomus How is it that these species can go virtually unchanged for millions of years?
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Admin
Director Posts: 13038 From: EvC Forum Joined: 06-14-2002 Member Rating: 2.1
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Message 2 of 29 (230921)
08-08-2005 10:00 AM
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Thread moved here from the Proposed New Topics forum.
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Chiroptera
Inactive Member
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Message 3 of 29 (230951)
08-08-2005 11:19 AM
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Reply to: Message 1 by Wolf
08-08-2005 9:57 AM
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The coelacanth that is alive today is definitely not the same as the ones that lived in the Mesozooic -- they aren't even in the same families. Lucy probably looked like a chimpanzee...to us. To a modern chimp, she may have not looked very much like a chimp at all. I wonder whether a primatologist can look at an austalopethicine skull and tell immediately that it is not a chimp. On the other, hand, if the modern chimp does look very similar to the ancient common ancestor she shares with modern humans, then I would venture to say that would be because the ancient ancestor and all the members of the chimp lineage have lived in the same kind of environment, in the same ecological niche, and so natural selection would have favored staying with a design that works. The rest of your list I don't know about. My guess is that either the ancient species and the current species lived in the same ecological niche and so natural selection would have weeded out those individuals that strayed too far from the very good design, or that, in fact, the species are far more different than you think.
| This message is a reply to: | | | Message 1 by Wolf, posted 08-08-2005 9:57 AM | | Wolf has replied |
| Replies to this message: | | | Message 4 by Coragyps, posted 08-08-2005 12:06 PM | | Chiroptera has not replied | | | Message 5 by Wolf, posted 08-08-2005 12:58 PM | | Chiroptera has replied |
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Coragyps
Member (Idle past 762 days) Posts: 5553 From: Snyder, Texas, USA Joined: 11-12-2002
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Message 4 of 29 (230970)
08-08-2005 12:06 PM
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Reply to: Message 3 by Chiroptera
08-08-2005 11:19 AM
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I wonder whether a primatologist can look at an austalopethicine skull and tell immediately that it is not a chimp.
My understanding is that they can, instantly. Hominid skulls have the spinal cord opening on the bottom, and chimps more at the back. The jaw is different, too.
| This message is a reply to: | | | Message 3 by Chiroptera, posted 08-08-2005 11:19 AM | | Chiroptera has not replied |
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Wolf
Inactive Member
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Message 5 of 29 (230995)
08-08-2005 12:58 PM
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Reply to: Message 3 by Chiroptera
08-08-2005 11:19 AM
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From what I have read about coelacanth, they have remained virtually unchanged for about 250 million years. I know today there are at least two different species of them. I have read this on scientific sites, not just creation sites. Lucy shared relatively the same environment as modern chimps. Mainly tree dwellers that could walk upright on the ground (main evidence, pelvis and spinal connection to the skull). Most evidence suggests they did not leave the trees for very long. Also they remained about the same for nearly 1+ million years, with very little change. Why would a chimpanzee not change through mutations and genetic drift, if they remained in practically the same environments as Lucy did? I understand that Homo erectus changed (speculated) into Neanderthal to the North (Europe/Asia) and Homo sapiens to the south in Africa. I realize Lucy might not look like a chimpanzee to other chimps, but we may view them like that. Heres a question for you. If a chimp and a human were put into cages side by side, strip away the clothes and reduce the human to grunts, would a visitor that had never seen either think we are two different species? Albeit one has less hair than the other... (A bit of topic) My other living fossils have remained pretty much unchanged for millions, 100+ million years. Why do mutations and genetic drift not affect them? Asexual reproduction has genetic mutations, they just do not occur as often as in sexual reproduction. Some or most of the listed species sexually reproduce. Bathynomus is found of off Australia, India and Mexico; all three are very similar to each, almost no change that is easily recognizable between them. They date back to when the continents were one landmass approximately 170 million years ago.
"A Dwarf on a Giants Shoulder sees the Furthest of the Two!"
| This message is a reply to: | | | Message 3 by Chiroptera, posted 08-08-2005 11:19 AM | | Chiroptera has replied |
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Chiroptera
Inactive Member
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Message 6 of 29 (231005)
08-08-2005 1:20 PM
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Reply to: Message 5 by Wolf
08-08-2005 12:58 PM
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quote:
From what I have read about coelacanth, they have remained virtually unchanged for about 250 million years.
I've read that, too. It's a big overstatement. -
quote:
Why would a chimpanzee not change through mutations and genetic drift, if they remained in practically the same environments as Lucy did?
First, I'm not sure that it's true that the chimp has not changed. Second, we are only speaking of a few million years. It is already well known that a species can undergo very little morphological change for five or ten million years or more. Third, if a species is already well adapted to a particular niche, then natural selection would actually tend to eliminate the variations that stray too far from the "typical" specimen (which, incidently, was the pre-Darwinian conception of natural selection).
| This message is a reply to: | | | Message 5 by Wolf, posted 08-08-2005 12:58 PM | | Wolf has replied |
| Replies to this message: | | | Message 7 by Wolf, posted 08-09-2005 9:55 AM | | Chiroptera has replied |
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Wolf
Inactive Member
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Message 7 of 29 (231292)
08-09-2005 9:55 AM
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Reply to: Message 6 by Chiroptera
08-08-2005 1:20 PM
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I have just read about another living fossil. Seed Shrimp, first fossils found in a stratum that dates back to 350 million years. There are 40,000 species of seed shrimp. Which is a lot considering there are about 8,700 birds and 4,100 mammals. Yet in 350 million years they are still only seed shrimp. Hagfish date back to 500 million years, there fossils contain no jawbone and living species today have no jawbones. I know if it fits the niche why change, it might be selected against. However you would think something better would have come along and out competed them in all those millions of years. Like placental's in North America did to South American marsupials some 4 to 5 million years ago. Source: In the Blink of an Eye, how vision sparked the Big Bang of Evolution, by Andrew Parker.
"A Dwarf on a Giants Shoulder sees the Furthest of the Two!"
| This message is a reply to: | | | Message 6 by Chiroptera, posted 08-08-2005 1:20 PM | | Chiroptera has replied |
| Replies to this message: | | | Message 8 by Chiroptera, posted 08-09-2005 12:27 PM | | Wolf has not replied |
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Chiroptera
Inactive Member
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Message 8 of 29 (231360)
08-09-2005 12:27 PM
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Reply to: Message 7 by Wolf
08-09-2005 9:55 AM
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quote:
There are 40,000 species of seed shrimp.
My bet is that every one of those 40,000 species are different that the ones that lived 350 million years ago. -
quote:
However you would think something better would have come along and out competed them in all those millions of years.
Actually (oops, sorry omnivorous), I wouldn't.
| This message is a reply to: | | | Message 7 by Wolf, posted 08-09-2005 9:55 AM | | Wolf has not replied |
| Replies to this message: | | | Message 10 by mick, posted 08-09-2005 8:05 PM | | Chiroptera has not replied | | | Message 16 by Omnivorous, posted 08-09-2005 9:27 PM | | Chiroptera has not replied |
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mick
Member (Idle past 5013 days) Posts: 913 Joined: 02-17-2005
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Message 9 of 29 (231634)
08-09-2005 7:52 PM
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Reply to: Message 5 by Wolf
08-08-2005 12:58 PM
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wolf writes: Lucy shared relatively the same environment as modern chimps Lucy (Australopithecus afarensis) existed in a wide variety of climates, quite dissimilar from contemporary chimps.
Bonnefille et al writes: For the entire 3.4- to 2.95-mya period, climatic parameters reconstructed from pollen indicate conditions significantly cooler and wetter than present, a conclusion that fits the depleted isotopic 18O values on shells (23), and may be partially explained by higher elevation (10). The mean temperature estimate of 20.2C calculated for all pollen samples implies that Hadar was generally 6.4C cooler than the present. This difference is consistent with an elevation 1,000 m higher than today, assuming a present lapse rate of 0.6C/100 m (24). Substantial temperature, rainfall, humidity, and biome change recorded in the upper part of sample 2, followed by a return to previous conditions, however, is not adequately explained by a unidirectional tectonic change. Indeed, subsidence in the Hadar area was virtually completed by the mid-Pliocene (25). Although variation in the climatic estimates between adjacent samples is generally encompassed within statistical error, the longer-term pattern of fluctuation implies a climatic cause (Fig. 3). The oldest level, just before 3.4 mya, shows highest probability precipitation values slightly greater than present, lower temperature, a higher humidity coefficient, and a higher WAMF biome score. After significant forest retreat, xerophytic biomes and STEP dominated, although buffered by a fluctuating swamp. Within the densely sampled interval 3.37—3.35 mya, strong cooling of up to 5C is associated with increasing rainfall of 200—300 mm/yr and a humidity index favorable to wet forest for a few thousand years. The pollen record of the upper SH and lower DD Members is more discontinuous but attests to the predominance of xerophytic biomes, although cooler and less arid than present (800—900 mm/yr; Table 3). The single pollen sample below the 2.95-mya BKT-2 indicates the return of higher humidity, slight expansion of the forest biome, and a greater difference between MTCO and Tann, which attests to a stronger seasonal contrast than today....We hypothesize that A. afarensis was able to accommodate to periods of directional cooling, climate stability, and high variability.
link So it simply isn't appropriate to say that Lucy existed in a similar environment to modern chimps.
wolf writes: I realize Lucy might not look like a chimpanzee to other chimps, but we may view them like that. Why may we view them like that? Lucy wasn't a chimp any more than we are chimps. Chimps weren't descended from lucy, and lucy wasn't descended from a chimp. Human beings didn't descend from chimps, and the idea that Homo sapiens is a direct descendant of Australopithecus afarensis seems unlikely. mick This message has been edited by mick, 08-09-2005 08:14 PM
| This message is a reply to: | | | Message 5 by Wolf, posted 08-08-2005 12:58 PM | | Wolf has not replied |
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mick
Member (Idle past 5013 days) Posts: 913 Joined: 02-17-2005
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Message 10 of 29 (231639)
08-09-2005 8:05 PM
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Reply to: Message 8 by Chiroptera
08-09-2005 12:27 PM
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chiroptera writes: My bet is that every one of those 40,000 species are different that the ones that lived 350 million years ago. Dead right. Wolf includes cockroaches as "living fossils" but there are over 4000 species of cockroach worldwide. It simply doesn't pass muster to claim that no evolution has occurred! Mick
| This message is a reply to: | | | Message 8 by Chiroptera, posted 08-09-2005 12:27 PM | | Chiroptera has not replied |
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Chiroptera
Inactive Member
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Message 11 of 29 (231641)
08-09-2005 8:08 PM
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Reply to: Message 9 by mick
08-09-2005 7:52 PM
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Hello, mick. If I may ask a question:
quote:
the idea that Homo sapiens is a direct ancestor of Australopithecus afarensis seems unlikely.
Why is this unlikely?
| This message is a reply to: | | | Message 9 by mick, posted 08-09-2005 7:52 PM | | mick has replied |
| Replies to this message: | | | Message 14 by mick, posted 08-09-2005 8:40 PM | | Chiroptera has not replied |
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jar
Member (Idle past 421 days) Posts: 34026 From: Texas!! Joined: 04-20-2004
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Message 12 of 29 (231643)
08-09-2005 8:11 PM
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Reply to: Message 9 by mick
08-09-2005 7:52 PM
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Garments and ancestors?
the idea that Homo sapiens is a direct ancestor of Australopithecus afarensis seems unlikely. Do you really mean ancestor?
Aslan is not a Tame Lion
| This message is a reply to: | | | Message 9 by mick, posted 08-09-2005 7:52 PM | | mick has replied |
| Replies to this message: | | | Message 15 by mick, posted 08-09-2005 9:13 PM | | jar has not replied |
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Nuggin
Member (Idle past 2520 days) Posts: 2965 From: Los Angeles, CA USA Joined: 08-09-2005
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Message 13 of 29 (231646)
08-09-2005 8:39 PM
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Changes over time
On the original question of why some species don't seem to evolve over time: There's an assumption here - that all change will show up in the fossil record. That's false. Chimps of today might look exactly like chimps from 350 million years ago (I doubt they do, but let's just pretend for a sec), but that doesn't mean they haven't changed at all. Today's chimps may be immune to diseases their ancestors couldn't handle. They may live several years longer. They may be more fertile, stronger, darker or lighter in coloring. They may have longer or shorter hair. They may be able to distinguish tastes their ancestors could not. Or, their spleens may be three times more efficient. All of the above is rank speculation. It's meant as examples of changes which could have happened that wouldn't show up in the fossil record. Even though the fossil record shows ample evidence of evolution taking place, there is plenty of change happening that doesn't leave it's mark when the creature dies. Also remember that not all benificial mutations are selected for. A chimp could be born which is faster, smarter, bigger and has a full functioning opposible thumb. Unfortunately, he's born into a troop of chimps living down wind from a sulfur spewing volcano. Oops. The process is very haphazard and big blocks of time aren't all that's needed for change to occur. On niches: A species which is doing especially well in a certain area - (ie cockroaches) is less likely to have genetic drift over time than a species struggling for survival. It's not that mutations occur less often, it's just that the forces driving selection are less influential. If food is abundant and danger rare, there is little advantage to cockroach one being slightly faster than cockroach two. If both live in the same swamp, they are both as likely to have offspring.
| Replies to this message: | | | Message 18 by Wolf, posted 08-10-2005 11:21 AM | | Nuggin has replied | | | Message 23 by gnojek, posted 08-10-2005 6:58 PM | | Nuggin has not replied |
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mick
Member (Idle past 5013 days) Posts: 913 Joined: 02-17-2005
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chiroptera writes: If I may ask a question:
quote:
the idea that Homo sapiens is a direct ancestor of Australopithecus afarensis seems unlikely.
Why is this unlikely?
Hi Chiroptera, Strangely enough, I'm citing the same paper in two different threads. In the land mammal to whale transition thread I mentioned a paper by Simon Tavare, who tries to assess the proportion of species which end up being fossilized. He finds that
quote:
no more than 7% of all primate species that
have ever existed are known from fossils.
So it seems unlikely to me that, of all the primates to have existed, one of the lucky 7% that happened to be represented in the fossil record is also the common ancestor. It just seems unlikely, given those odds, that the oldest fossil we happen to have discovered is also the REAL ancestor of humans, rather than a sideshoot of some unknown ancestral branch. Mick This message has been edited by mick, 08-09-2005 08:41 PM This message has been edited by mick, 08-09-2005 08:43 PM
| This message is a reply to: | | | Message 11 by Chiroptera, posted 08-09-2005 8:08 PM | | Chiroptera has not replied |
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mick
Member (Idle past 5013 days) Posts: 913 Joined: 02-17-2005
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Message 15 of 29 (231659)
08-09-2005 9:13 PM
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Reply to: Message 12 by jar
08-09-2005 8:11 PM
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Re: Garments and ancestors?
Thanks - I edited my post! mick
| This message is a reply to: | | | Message 12 by jar, posted 08-09-2005 8:11 PM | | jar has not replied |
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