Controversies in Science/What killed the dinosaurs/A Critique of Environmental versus genetic sex determination: a possible factor in dinosaur extinction?

(Review Paper) Cited in Controversies in Science/What killed the dinosaurs/A Critique of Environmental versus genetic sex determination: a possible factor in dinosaur extinction?

Points Made

Studies show in current extinction patterns, that the sex ratio changes for TDS (Temperature-Dependent sex determination) animals changes based on significant climate change. This could also be true for the extinction pattern of dinosaurs which may have resulted in the preponderance of males .

In laboratory experiments, scientists found that they could control what sex a reptile embryo would develop into based on what temperature the embryo was exposed to. The temperature-sensitive switch that determines male or female varies depending on species but all reptile embryos that use TSD, such as dinosaurs, have this critical incubation time

Scientists can control whether there will be and all male or all female hatching depending on the constant temperature.

65 mya years ago a meteorite may have hit the earth, but it is more likely that the constant volcanic eruptions 31-34 mys drastically changed the temperature of the earth. The falling temperature would have affected the incubation of TSD-dependent reptile eggs.

Even a minor increase or decrease in present day temperature has been shown to have endangered some turtle species.

Methods

Through molecular relationships, it has been determined that TSD achieves its sex ratio through temperature s in two separate ranges, below intermediate and above intermediate. This proved, that dependent on the species, and seen in dinosaurs, that certain embryos would develop as the male or female sex (generally whichever was the more dominant in the species). Note that TSD is persistent in reptiles .

Results

Based on phylogenetic evidence, as well as the latest molecular genetic data, it has been determined that dinosaurs are a TSD species. TSD species have been shown to be affected by significant climate change which may have caused the procreation of an abundance of male dinosaurs with few females to continue the species .

In addition, mathematical evidence proves that temperature sensitive species, including dinosaurs, would be negatively affected by climate shift. This is especially significant in species with a slow recovery rate, and the birth and death rates after extreme climatic and environmental changes .