? for Theistic Evolutionists

[learning]

I have a ? or two.

How far back can they trace some of the plants and animals we have today? I guess, what I'm really asking is, how far back to the first multi-cellular animal, mammal, bird, fish etc? Want a rough idea of the time spread. Thanks

What is the earliest living life form on earth that we know of? Bacteria? Anything else?
How old is it?

[bigsplit]

Here is a link.

http://www.talkorigins.org/origins/geo_timeline.html, First one to pop up in a google search.

[learning]

Thank you very much. From what I understand, the first living life forms were Prokaryotic cells, cells without membranes, or thin membranes, then blue-green algae and Archaea are really intersting (the things that live in hot geisers, thought to have existed at the beginning of our world) and then Eukaryotic cells, cells with membranes with things inside, like nucleus, with membranes around them too.

Then came multi-cellular organisms. Then Ediacaran - soft bodies, like worms or other type of creatures(of which I've read the largest fossils of these in the North West Territories of Canada in the MacKenzie Mts.)Then the Cambrium explosion, (hard bodied creatures) where they say the ancestor of everything alive today may have come from just before that period.(that's as far as I've got, but saw the basic dates for some of these)

Really good link I found that shows pictures of some of the things mentioned here
http://geol.queensu.ca/museum/exhibits/dawnex.html

[lucaspa]

Thank you very much. From what I understand, the first living life forms were Prokaryotic cells, cells without membranes, or thin membranes, then blue-green algae and Archaea are really intersting (the things that live in hot geisers, thought to have existed at the beginning of our world) and then Eukaryotic cells, cells with membranes with things inside, like nucleus, with membranes around them too.

1. Prokaryotes have no NUCLEUS. That is, no separate organelle where the DNA is kept. They do have membranes. Most also have a cell wall, outside the membrane. The cell wall is made up of carbohydrates -- molecules made out of many sugar molecules.
2. Some of the first fossils are stromatolites, which are a form of bacteria. The first fossils actually look a lot more like protocells than bacteria.

Then came multi-cellular organisms. Then Ediacaran - soft bodies, like worms or other type of creatures(of which I've read the largest fossils of these in the North West Territories of Canada in the MacKenzie Mts.)

Eidacaran are a special branch of soft-bodied. Actually, Eidacaran denotes more the formation in which the fossils were found rather than the type. Most of the species in the Eidacaran do not have descendents.

However, some of the soft-bodied fossils of the same time -- but not in the Eidacaran sediments -- do seem to be the ancestors of modern worms and other multicelled organisms.

Then the Cambrium explosion, (hard bodied creatures) where they say the ancestor of everything alive today may have come from just before that period.(that's as far as I've got, but saw the basic dates for some of these)

Most living things are bacteria and Archaea. That means that most living things have ancestors that are NOT the multicelled animals in the Cambrian. What we have for the Cambrian are the first species that clearly belong to MOST (not all) of the modern phyla. That is, the first species that we can tell are mollusks, the first vertebrates, etc.

[lucaspa]

I have a ? or two.

How far back can they trace some of the plants and animals we have today?

Depends on what you mean by "trace". If you mean individuals back through species, then the answer is about 10 million years. But that varies from species to species. Humans, for instance, can be traced by individuals back thru 2 other species to A. afarensis about 3-4 million years ago.

Now, if you mean by transitional SPECIES (that is species that connect higher taxa like genus, family, and class), then all life can be traced back to 3.8 billion years ago.

In terms of the ancestor to amphibians, reptiles, and mammals, we have a candidate common ancestor in the Carboniferous:

2. J A Clack, A new early Carboniferous tetrapod with a melange of crown-group characters Nature 394, 66: 1998 (July 2).
4. H Gee, Relics: The creature from the black lagoon
http://www.nature.com/Nature2/serve?...update662.html Transitional fossil between amphibians, reptiles, and mammals.

[qoute]I guess, what I'm really asking is, how far back to the first multi-cellular animal, mammal, bird, fish etc? Want a rough idea of the time spread. Thanks [/quote]
4. GJ Vermeij, Animal origins, Science 274: 525-526, 1996 (Oct. 25). The peer-reviewed article is GA Wray, JS Levington, and LH Shapiro, Molecular evidence for deep precambrian divergences among metazoan phyla. Science 274: 578-573, 1996 25 Oct.
5. RA Kerr, Pushing back the origin of animals, Science 279: 803-804, 6 Feb. 1998. The peer reviewed article is C-W Li, J-Y Chen, T-E Hua, Precambrian sponges with cellular structures. Science 279: 879-882. Got embryonic animal fossils that lived 40-50 million years before the Cambrian. Correlates with the molecular data and removes the Cambrian "explosion".
6. RA Kerr, Tracks of billion year old animals? Science 282: 19-20, Oct. 2, 1998. Primary article is A Selachner, PK Bose, F Pfluger, Triploblastic animals more than 1 billion years ago: trace fossil evidence from India. Science 282: 80-83, Oct. 2, 1998. Shows tracks of worms 200-500 million years before Cambrian.

[grmorton]

6. RA Kerr, Tracks of billion year old animals? Science 282: 19-20, Oct. 2, 1998. Primary article is A Selachner, PK Bose, F Pfluger, Triploblastic animals more than 1 billion years ago: trace fossil evidence from India. Science 282: 80-83, Oct. 2, 1998. Shows tracks of worms 200-500 million years before Cambrian.

You should be aware that this is still a controversial site.

[lucaspa]

You should be aware that this is still a controversial site.

Yes, there have been criticisms of that piece of data. Whether it is really worm tracks or not. But it's one place among many for Learning to look at data tracing multicellular mobile animals back to 1 billion years ago.