Human Pregnancy Linked to Egg-Laying Animal 300 Million Years Ago

Human pregnancy has been linked to an egg-laying animal, similar to the duck-billed platypus, that lived 300 million years ago.

According to new research by scientists from UCL and Yale University and published in Biology Letters, platelet cells, which prevent non-stop bleeding, evolved about 300 million years ago in the egg-laying animal, paving the way for mammals including humans to develop a placenta, which is necessary for pregnancy. 

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The researchers said the platelet cells were necessary for the evolution of eutherian mammals including humans, because they prevented the mother from hemorrhaging while delivering a baby.  According to the scientists, the egg-laying mammal started creating platelet cells potentially by chance. They were then passed on to other animal groups. The group became the first mammals about 300 million years ago. The duck-billed platypus is a descendent of these mammals. 

"We have shown with convincing evidence that platelets occurred 300 million years ago even before monotremes arose. This unique feature subsequently allowed the placenta to develop, which led to the eutherian mammals and therefore human beings," UCL Professor of Cardiovascular Medicine, John Martin said in the report. "During birth, safe disconnection of the placenta from the uterus is essential for the survival of the mother and child, so without platelets, neither would have survived and the evolutionary step to eutherian mammals, including human beings, would never have happened."

Research Came Out of the YAL UCL Collaborative 

The research was done as part of a collaboration between YAL and UCL called the Yale UCL Collaborative. Created ten years ago, it promotes joint research. Martin said that through the collaborative he was able to work with Yale Professor of Ecology and Evolutionary Biology Günter Wagner, a leading expert in evolutionary biology.

"The unique presence of platelets in mammals explains why deeply invasive placentation is limited to mammals, even though live birth is found in many other animal lineages, but not invasive placentation," Wagner said in the report. 

The researchers aren't the only ones looking at pregnancy. In February a study revealed that positive thinking during pregnancy could lead to children who are better at math and science. Scientists at the University of Bristol studied 1600 pregnant women beginning in the 1990s and found women that believe they have control over the outcomes of their lives are more likely to have children who were good at science. Those mothers were more likely to support children as they pursue their academic work relating to science.