Geneticist from the University of Chicago found when the ancestors of mammals (and humans) initially are animals that lay eggs. However, about 185 years ago, for the first time appeared mammals give birth to a child. As humans today.
Based on genetic research conducted in the womb cats, dogs, chickens, lizards, and frogs, mammals have revealed when 2,502 new genes make it evolve childbearing.
Thousands of genes called "gene jump 'who claimed to be the cause of the evolution of the mammalian uterus and stop the habit of laying eggs. Gene called jump, because genes had originally come from other parts of the body which eventually joined in the womb.
"The results of our study indicate if there is a major change in the birth of mammals. The change was influenced by the addition of new genes in the uterus from the other organs of mammals," said Dr. Vincent Lynch, an evolutionary geneticist at the University of Chicago, the Daily Mail (30/01)
Not only that, the genes jump also helps the baby to grow and survive from the mother's immune system without having to use a shell like a baby bird eggs.
However, currently there is not a single species of mammals that evolved and still gives birth by laying eggs, the platypus. Endemic to Australia is both a proof when initially mammals lay eggs.
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