Thursday, April 12, 2012

Could 'advanced' dinosaurs rule other planets?

This is the title of a short article at PhysOrg. What it basically starts with is:
New scientific research raises the possibility that advanced versions of T. rex and other dinosaurs — monstrous creatures with the intelligence and cunning of humans — may be the life forms that evolved on other planets in the universe. "We would be better off not meeting them," concludes the study, which appears in the Journal of the American Chemical Society.
The evolutionary biology courses that I took (waaaaay back in biology class) tell us the short answer: No, 'advanced' dinosaurs couldn't rule other planets. (Sorry to all those pulp sci-fi novels from the '50s.)

Longer answer: they may be LIKE dinosaurs (and might even appear roughly like what we might call a dinosaur), but not like the dinosaurs that we think we know.

Longer-still answer: it is next to impossible that conditions exist to create Earth-like dinosaurs on a different planet, since it would require that conditions exist to select for the organisms that led ultimately to dinosaurs. This isn't a StarTrek-like universe in which various species' DNA are - strangely and paradoxically - compatible with each other.

In other words, given an ecosystem, it is possible (over time) for creatures to evolve to have physiques that are best suited to their environments (both physical and biological). It is not surprising, therefore, that javalinas look like pigs: they fill a similar niche as pigs in the Old World. It's not odd that there were dog-like marsupials, as well as (in prehistory) saber-toothed tigers that were marsupials and placentals, filling similar niches, looking relatively similar, but living in very different epochs (the Miocene and the Pleistocene, respectively).

... but why is this being reported in the Journal of the American Chemical Society? Well, the paper is not actually about dinosaurs:
n the report, noted scientist Ronald Breslow, Ph.D., discusses the century-old mystery of why the building blocks of terrestrial amino acids (which make up proteins), sugars, and the genetic materials DNA and RNA exist mainly in one orientation or shape. There are two possible orientations, left and right, which mirror each other in the same way as hands. This is known as "chirality." In order for life to arise, proteins, for instance, must contain only one chiral form of amino acids, left or right. With the exception of a few bacteria, amino acids in all life on Earth have the left-handed orientation. Most sugars have a right-handed orientation. How did that so-called homochirality, the predominance of one chiral form, happen?

Breslow describes evidence supporting the idea that the unusual amino acids carried to a lifeless Earth by meteorites about 4 billion years ago set the pattern for normal amino acids with the L-geometry, the kind in terrestial proteins, and how those could lead to D-sugars of the kind in DNA.
So, it is possible, therefore, that such amino acids also landed elsewhere, and it is possible that these amino acids also went through the process leading to multi-cellular life, and it is possible that this multi-cellular life produced ecosystems that gave rise to things that look kind of like dinosaurs.

... or something.

(I think that the connection to dinosaurs is really tenuous; more like a "hey, our research has some relevance" statement, because talking about possibly advanced dinosaurs is far more interesting to a general audience than talking about left-handed vs. right-handed amino acid orientations and the origins of said amino acids.)

... and what PZ Myers said (with much better focus and snark).

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