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The loss of anatomical features is a frequent evolutionary event. For example, humans and other great apes lost their tails and whales lost their legs. The most convincing evidence comes from the presence of remains in the fossils. Unfortunately, the fossil record mainly retains remnants of hard structures such as bones or teeth. Therefore, the resolution of the evolution of soft tissue structures such as muscle or brain tissue requires analytical methods. A team of researchers from the Max Planck Institute for Molecular Biology and Genetics, the Max Planck Institute for Complex Systems Physics, the Senckenberg Natural History Collections of Dresden and the Museum of Art. Frankfurter's natural history offers a new approach to solving -fabric structures, with a focus on testicular evolution in mammals.
Solving the evolution of soft tissue structures, crucially depends on the precise knowledge of evolutionary relationships between the species considered. If these relationships are not completely resolved, the evolution of soft tissue structures remains uncertain. Michael Hiller, affiliated with the two institutes Max Planck and the Center for Systems Biology Dresden, says: "Instead of directly studying soft tissue structures, we traced the evolution of genes necessary for their formation. "
their investigation, the researchers used the descent of the testicles as an example. In almost all adult mammals, the testes are located in the scrotum or the lower abdomen. But the testes initially grow deep in the abdomen at a position close to the kidneys, as seen in mammalian embryos. The final position of the testicles is the result of a descent process that occurs during the development of the animal. However, many African species such as elephants, tenrecs, golden moles, elephant shrews, manatees and rock hyraxes differ from other mammals in having no descent and having testicles at their disposal. their initial abdominal position. It is an open question whether these African species have lost the process of testicular descent or if other mammals have gained this characteristic. Thomas Lehmann of Senckenberg Frankfurt adds, "The evolution of testicular offspring is controversial because it is not completely understood how African species are related to other mammals."
Nonfunctional Genes
"To resolve this controversy, we analyzed DNA sequence data from 71 mammals and found that these African mammals have nonfunctional residues of two genes strictly required for descent. testicular in other mammals, "says Virag Sharma, the first author of the study.This shows that the functional versions of these genes were once present in the ancestors of African mammals that do not have any Testicular offspring today These "molecular vestiges" suggest that the process of testicular descent took place in the ancestor and was subsequently lost in African mammals. "Important, this finding takes into account ongoing controversies on the evolutionary relationships between mammals "explains Heiko Stuckas of Senckenberg, Dresden." The increasing availability of DNA sequence data from many The species offers unprecedented opportunities to hunt molecular remnants and thus resolve debates about the evolution of other anatomical traits, "concludes Michael Hiller, who oversaw the study.
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