All present-day life arose from a single origin

All present-day life arose from a single origin

One isn’t such a lonely number. All life on Earth shares a single common ancestor, a new statistical analysis confirms. The idea that life-forms share a common ancestor is “a central pillar of evolutionary theory,” says Douglas Theobald, a biochemist at Brandeis University in Waltham, Mass. “But recently there has been some mumbling, especially from microbiologists, that it may not be so cut-and-dried.” Because microorganisms of different species often swap genes, some scientists have proposed that multiple primordial life forms could have tossed their genetic material into life’s mix, creating a web, rather than a tree of life. To determine which hypothesis is more likely correct, Theobald put various evolutionary ancestry models through rigorous statistical tests. The results, published in the May 13 Nature, come down overwhelmingly on the side of a single ancestor. A universal common ancestor is at least 102,860 times more probable than having multiple ancestors, Theobald calculates.

I had always wondered if life all stemmed from one source. I thought you all might fin this interesting as well.

Source

[edit on 13-5-2010 by Raustin]

Theobald’s study does not address how many times life may have arisen on Earth. Life could have originated many times, but the study suggests that only one of those primordial events yielded the array of organisms living today. “It doesn’t tell you where the deep ancestor was,” Penny says. “But what it does say is that there was one common ancestor among all those little beasties.”

Same source, not so veiled self bump.

Having read the actual article in question.. nowhere does he dispute that "tree of life" should rather be a "web of life" as horizontal gene transfer is so common among prokaryotes and has played a major part in eukaryote evolution as well (there was an article about this in last week's nature) and in recent human evolution too (latest science, announcement of sequenced Neanderthal genome). I recently read another fascinating article (some low impact journal) about LUCA. This guy argued that first cellular life was bacterial and that archaea and eukaryotes actually developed from gram-positive bacteria some 850 million years ago and ton of horizontal gene transfer followed (instead of LUCA being an ancestor of all 3 domains). ..would love to see some statistical analysis on that hypothesis

[edit on 13-5-2010 by rhinoceros]

I wonder if there could ever be any kind of practical discussion about origins of all life that is not about some single source.

This is simple, we just exist with no end and no start. There is no single source unless there were events somehow before it that lead to such an effect where the cause is basically forgotten, lost, or impractical to reach for discovery.