Human embryos have extra lizard-like muscles in their hands | 10/10/2019 | Eleanor Imster
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Scan of the left hand of a 10-week-old human embryo. The dorsometacarpales are highlighted: these muscles are present in adults of many other limbed animals, while in humans they normally disappear or become fused with other muscles before birth. Image via Rui Diogo, Natalia Siomava and Yorick Gitton.

New research shows that some muscles, thought to have been abandoned by our mammalian ancestors 250 million years ago, never completely went away.

Team - Biologists - Limb - Muscles - Remnants

A team of evolutionary biologists have demonstrated that numerous atavistic limb muscles – remnants of anatomy that evolution never completely ditched – are actually formed during early human development and then lost prior to birth. According to the study, published October 1, 2019, in the journal Development, they are probably among the oldest, albeit fleeting, remnants of evolution yet seen in humans.

Some of these muscles, such as the dorsometacarpales shown in the image above, disappeared from our adult ancestors more than 250 million years ago – a relic from when reptiles transitioned to mammals. The scientists aren’t sure why the human body makes and then deletes them before birth.

Biologist - Rui - Diogo - Howard - University

Evolutionary biologist Rui Diogo of Howard University led the study. Diogo told the BBC:

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Statement - Researchers - Study

According to a statement from the researchers about the study:

Remarkably, in both the hand and the foot, of the 30 muscles formed at about 7 weeks of gestation one third will become fused or completely absent by...
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