As a measure of the development speed, the researchers chose the number of generation sequences needed, because only in this case, new gene variants that allow development to more size arise. This is the deciding factor in evolution, not time, explain Alistair Evans and his colleagues. The generation sequence as a measure also allowed a meaningful comparison between life forms with different lifetimes. The model researchers finally came to the maximum development speed of the property body mass: For an increase in size, which corresponds to that between a mouse and an elephant, the evolution of land mammals therefore requires at least 24 million generations. If, on the other hand, a certain size had already been reached, it was obviously faster: An already rabbit-sized animal species required about ten million more generations before a species with elephantine dimensions could emerge.
Whales became giants comparatively fast
An exception to the rule revealed in the study of the evolution of the whales: The evolution of small marine mammals to the giants of the oceans was carried out twice as fast as the studies in the land mammals. The researchers suspect that increasing the size of the water, because of the load-bearing properties of the medium, requires less costly adjustments than on land. To the "model"? To evolve an elephant, evolution must master severe static challenges, believe Alistair Evans and his colleagues. display
The researchers also examined the speed of the opposite development in their investigations? How many generations are needed to develop a smaller one from a large animal species? An example of this are today's dwarf forms of the hippo or the elephants and mammoths that once existed on some islands. Here, fossils from the genealogical tree of these species document that the shrinkage was comparatively fast: The development of the pygmy elephants, for example, took ten times less generations than the reverse evolution of a sheep-large ancestor of elephants to the large species.Alistair Evans (Monash University School of Biological Sciences, Australia) et al .: PNAS, doi: 10.1073 / pnas.1120774109 © science.de? Martin Vieweg