Monday, September 21, 2009

Evolution of the Four-Chambered Heart

Creationism lost another icon today when it was announced by the Gladstone Institute for Cardiovascular Disease that a gene in the four-chambered heart can be traced to turtles and other reptiles. E-Science News writes:

"This is the first genetic link to the evolution of two, rather than one, pumping chamber in the heart, which is a key event in the evolution of becoming warm-blooded," said Gladstone investigator Benoit Bruneau, PhD, who led the study. "The gene involved, Tbx5, is also implicated in human congenital heart disease, so our results also bring insight into human disease."

From an evolutionary standpoint, the reptiles occupy a critical point in heart evolution.

It has always been a tenet of creationism that the four-chambered human heart could never have evolved by itself and that this constitutes evidence against evolution. The writer continues:
During evolution, new genetic regulatory elements evolved to tell the Tbx5 gene to form a sharp boundary of Tbx5 expression. This resulted in two ventricles. Researchers will now work to identify those genetic regulatory mechanisms during the evolution of reptiles. The work also has important implications for the understanding of congenital heart defects, which are the most common human birth defect, occurring in one out of every one hundred births worldwide. Humans born with only one pumping chamber, resembling frog hearts, suffer the highest mortality and require extensive surgery as newborns.
As Kenneth Miller says: "Never bet against science."

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