Home » science » Weird Science Day 18: The Last Universal Common Ancestor

Weird Science Day 18: The Last Universal Common Ancestor

Remember how mad they were at Darwin? Humans related to the apes? Piffle! They drew cartoons of Darwin as a chimp. Can you imagine if they got a hold of this LUCA theory? I mean, bad enough we’re related to, ugh, monkeys, but to be related to every other single organism–including fungus–on Earth. That’s a bitter pill to swallow.

LUCA stands for Last Universal Common Ancestor. It is a single cell from which all life as we know it arose. Life came about only once on Earth; it turned into  LUCA and then into me and you and everyone we know.

And we know this how? Well, because all life on Earth shares the genetic code. It all contains DNA. Here’s how the actionbioscience site puts it:

“That the genetic code is universal to all life tells us that everything is related. All life regenerates itself by producing offspring, and over time small changes in the offspring result in small changes to the protein recipes. But because the recipes are written in the same language (the genetic code), it is possible to compare these recipes (and other genes) to build the equivalent of a family tree.”

What that means is that our working parts are interchangeable. “…a gene from a human being can be put into a bacterium, and the bacterium will make the human protein…”

See what I  mean.

So as per LUCA theory, we have a new family tree. It’s up there in today’s image if you’d like to see what it looks like. LUCA’s in the center. The pink lines emanating from LUCA represent the evolutionary branches that have produced all of today’s species. These species exist in three domains represented by the colored sections of the outer ring.

Just so you know, the green part of the ring represents the archaea group. Archaea are single celled organisms without a true nucleus. The pink part of the ring is the group called “eukaryota.” That’s us, by the way. Beings with true nucleated cells. Eukaryotes include all the common animals that we know, all the common plants we know and tons of animals and plants that are not familiar at all, such as amoeba, fungus, etc. Then there’s the purple-blue part of the ring. Whoever is in this group is blessed indeed for they appear to be taking over the world. That, my friends, is the bacteria group, a prolific bunch.

So what was this universal common ancestor, this cell, like? According to Science Daily, “Many believe LUCA was little more than a crude assemblage of molecular parts, a chemical soup out of which evolution gradually constructed more complex forms. Some scientists still debate whether it was even a cell.” The article goes on to say that might not be the case. LUCA may have been a definite cell indeed, complex even. Lots of organelles and processes going on.

According to New Scientist, LUCA was “enormous: a mega-organism like none seen since, it filled the planet’s oceans before splitting into three and giving birth to the ancestors of all living things on Earth today.” Before LUCA, the oceans were a “global genetic swap shop.”  Cells exchanged genetic material not for the competition that drives Darwinian competition but simply to survive. Eventually, one global mega-organism arose: LUCA.

That’s the theory anyway.  I can’t imagine how they’re going to prove it one way or another, but it’s fascinating to imagine.

Thanks for reading.

Sue Lange’s latest ebook, Tritcheon Hash, is full of lapses of logic and weird science. “It’s a wild, good read.” Get your copy from Amazon or read a couple of free chapters at the publisher’s website.

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3 thoughts on “Weird Science Day 18: The Last Universal Common Ancestor

  1. I’d have to read up on it a bit more, but I’m not inclined to believe in a single super-organism that split into three.

    I reckon that back then, life was too random to be that organised. I do think that life evolved from a single species, that evolved from the chemical soup of the primordial world once it had cooled down enough for those chemical processes to begin.

    This is a bit too close to the ‘one true god and the trinity’ mythology for me to take without several grains of salt.

    What thinkest thou?

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