The traditional approach to unraveling the evolutionary past of an organism has been to study its fossils. It makes sense: what better way to learn about who and what a creature came from than to look at its forerunners? But more recently, scientists have been looking to genetic research to determine what exactly the changes were that the DNA of these organisms went through to get from point A to point B. In particular, scientists use developmental genetics, or the study of how an organism’s genetic code coordinates the development of its embryo, to determine which species have similar developmental patterns and how they may be related or share a common ancestor. A new study did a review of analyses that take it one step further: using both paleontology and genetics, a group of researchers has tracked the evolution of a number of organisms we all are familiar with, including dolphins, whales, snakes, elephants, and mice.
The research group, led by led by Dr. Hans Thewissen from the Northeast Ohio Medical University, surveyed a number of studies that analyzed DNA in order to shed light on fossil remains. They found that the change in morphology that two chronically consecutive fossils exhibit often seems like a big and complicated transformation, when in fact it represents a small genetic change. If one piece of DNA is turned off or on, or a piece cut out of or added to the genetic code, the morphology of an organism can completely transform. For example, whales probably evolved from a four-legged ancestor—this evolution, however, only took a few changes in the genetic code and a couple intermediary ancestors, and, wah-lah, a walking four-limbed organism became a swimming, limb-less one.
The new research also looks at studies on developmental mechanisms—how an animal’s genes give rise to embryonic development, and how that development leads to that organism’s shape. Some of these mechanisms are present across different organisms; and one organism’s genes can act out many different mechanisms. For example, a snake evolved to be limb-less through two different mechanisms. It lost its neck region, also losing the limb buds that would form during development had the neck region existed. The hind limbs, however, do bud; but the genes that mastermind their development cease their growth before they exist.
The NEOMED team also revealed that scientists can change the genes of a living organism to simulate transformations seen in the fossil record. Modern elephants have teeth that are over a foot longer than those of their early ancestors, as observed in the fossil record. How did this change occur on a genetic level? Scientists can manipulate the genes of laboratory mice to make their teeth grow larger, reflecting the same change they see in the fossil record of elephants, thus elucidating the mechansims by which ancient elephents evolved into modern ones.
“It is a very exciting time to be an evolutionary scientist,” said Dr. Thewissen, “So many researchers are investigating evolution, either by finding new fossils or by figuring out the genes that underlie changes in evolution. Now it is possible to combine those two fields and go beyond what each field could have accomplished on its own.”
Read more about this exciting new cross-disciplinary approach at www.redorbit.com.
This study was published in the Journal of Vertebrate Paleontology.
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