Friday Headlines, February 6, 2015
THE LATEST IN THE GEOSCIENCES
New World monkeys are not all that new.
We’ve seen the bottom of a tectonic plate!
An organism that hasn’t evolved in two billion years.
A recent discovery of a fossil primate in South America has forced some adjustments about how we thing the so-called New World monkeys came into existence.
This finding, some fossilized teeth from rocks approximately 36 million years old, are fossil monkeys most closely related to other similarly-aged primates in Africa.
The next question to answer is how the monkeys got from Africa to South America.
I’m always a little put off by the indirect reference to ‘scientists.’ Why not geologists or geophysicists? Or is that too hard for people?
But I digress. I’ve talked a couple of times (here and here) about what plates are, these big thick chunks of the Earth’s surface that move around and interact to make volcanoes, earthquakes, mountain ranges, and great, deep valleys. Now, using geophysical methods, geologists have gotten a picture of what the bottom of a plate looks like, and more importantly how it interfaces with the rock beneath.
Why should we care? Understanding the way the lithosphere relates to the underlying asthenosphere tells us a lot about how the Earth works as well as its history. And understanding that could help us do a better job of knowing what might happen in the future.
So, what did they discover? They found an approximately 6-mile thick layer of rock that has very low viscosity, making it rather slippery such that the overlying lithosphere might just slide over the surface. If plates slip easily over the asthenosphere, this means that some hypotheses to explain the motion of plates might not be true.
Who are these ‘scientists’? Are they the same ones that imaged the base of a plate?
Oops. I digressed again.
I admit to being skeptical whenever the claim is made that something hasn’t evolved over some interval of geologic time. Of course it’s evolved. It just doesn’t look different. So, let’s see what they really have.
So the organism in question is a type of bacteria that can utilize sulfur in place of oxygen. Using various methods, the scientists – this time geomicrobiologists – determined that the physical appearance of the modern bacteria is identical to that of fossil examples more than two billion years old. They also determined that the fossil bacteria inhabited environments similar to that preferred by the modern example.
The researchers hypothesize that there’s no apparent change in the organisms because there’s no selective pressure for change. That is, these bacteria are well suited for their environment, and they aren’t competing against other bacteria, so there’s no reason for them to change, other than genetic drift (truly random changes that neither help nor harm organisms). With no selective pressure, there’s not reason for the organisms to change in shape.
However, I have a suspicion that if we could get DNA from the 2 billion year old examples, they’d be quite different genetically. Alas, there will be no DNA and my hypothesis can never be tested.