General Chat

Some people investigate the previous two or three generations of their family; others trace their ancestors over many centuries. But when it comes to extreme genealogy, none can compete with a group of scientists trying to find out about the ancestor of all life.

Every living thing on Earth - from humans to bacteria, from bluebells to blue whales - is thought to be descended from one single entity, a sort of primitive cell floating around in the primordial soup three or four billion years ago. So what did it look like? How did it live, and where? Named the "last universal common ancestor", or LUCA for short, it has left no known fossil remains, nor any other physical clues to its identity. For a long time, questions about LUCA were thought beyond the reach of science.

But LUCA could enjoy a resurrection at last. Researchers are comparing the genes of all kinds of life to draw a portrait of this mother of us all. Their findings are the subject of huge controversy and are challenging some of the most basic assumptions about primordial life. There is evidence, for example, that early evolution was driven by forces very different to those we usually associate with natural selection. Another surprise is that DNA, life's code book, may have evolved on two separate occasions. "This is very exciting," says Anthony Poole of Stockholm University in Sweden. "It changes our picture of LUCA extensively."

It was in the mid-1800s that Charles Darwin first focused attention on our distant ancestry by setting out his theory of evolution by natural selection. He proposed that similar species had common ancestors and so shared a family tree. But Darwin could not decide whether all living creatures belonged to one such tree or several.

It was only in the 1950s and 60s that efforts to probe the most basic operations of cells began unveiling the similarities that link all life forms. Almost every organism, for example, uses long strands of deoxyribonucleic acid, better known as DNA, to encode the countless proteins required to build and sustain life. They also use short lengths of a similar molecule called ribonucleic acid (RNA) for retrieving the information stored in DNA one gene at a time, to allow the proteins to be manufactured. And without exception all life forms use large and complex molecular machines known as ribosomes to use those RNA snippets as templates for assembling proteins out of amino-acid building blocks.

Perhaps the most telling evidence for a single common ancestor is the shared language of our genes. Although there seem to be no biochemical reasons why certain "letters" of DNA or RNA should encode certain amino acids, the same codes are used across the tree of life, with only a few exceptions (New Scientist, 30 August 2003).

Sheesh Len!

Why do you always throw up something of interest when I don't have the time to digest properly?

Come to that.....How come you are so much younger than me when it comes to cognitive thought?......another thread I will have to bookmark til the time is right! ...sigh!

It is very difficult to find any documents from when we were in the primordial soup,may have been lost in the blitz like a lot of others,or just got wet in the soup.Who knows?

Did mine about two hundred years a long time ago but have recently picked out interesting little bit to look deeper into.

Fascinating Len and however far we go back there are always the same questions of where did the oldest thing come from and why did it happen. Future generations will no doubt find the answers to much that puzzles us now.