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Our platelet cells, which prevent us from bleeding all the time, evolved 300 million years ago

Posted July 17, 2019

Everything in nature is interrelated. Evolution gave us incredible capabilities and pretty good bodies, but some features that we enjoy were actually evolved by other organisms. For example, according to a new UCL and Yale University study, platelet cells, which prevent mammals from bleeding non-stop came from an egg-laying animal similar to the modern duck-billed platypus.

Platelet cells, which made eutherian mammals, including modern humans, possible, were evolved in an egg-laying animal similar to the modern duck-billed platypus around 300 million years ago. Image credit: John Gould via Wikimedia

Platelet cells are crucially important for our survival. They clot blood caused by cuts or lesions, preventing us from bleeding out from relatively minor injuries. For example, if not platelet cells every mother would die when giving birth. Eutherian mammals, including humans, have deep invasive placenta (haemochorial placentation). Without platelet cells haemorrhaging at birth would be a normal thing. However, these platelet cells did not actually involve in humans.

Scientists conducted a study and found that platelet cells evolved around 300 million years ago in an egg-laying animal similar to the modern duck-billed platypus. Scientists believe that evolution of these cells could have occurred by chance, but either way, they were passed on when this animal group diverged around 300 million years ago into monotremes (the first mammal group) and eutherian mammals, which include modern humans. So this is basically how we got our ever so important platelet cells, but that’s not all – if they didn’t exist, we wouldn’t exists.

Platelet cells allowed the placenta to develop, which led to the eutherian mammals and therefore human beings. John Martin, one of the authors of the study, said: “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”.

Scientists say that this explains why deeply invasive placentation is limited to mammals, even though other animals feature live birth too. We simply got this feature from a common ancestor 300 million years ago. Platelet cells are a crucial part of the evolution of placenta and it made us, eutherian mammals, possible. This research is useful as it explains a small part of our evolution, which may lead to bigger, more significant discoveries.


Source: UCL

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