Your oldest ancestor was really weird and had a big mouth

By Will Dunham | WASHINGTON

Don’t take this the wrong way, but your oldest ancestor was not exactly a beauty.

Scientists on Monday said a tiny marine creature from China that wriggled in the seabed mud about 540 million years ago may be the earliest-known animal in the lengthy evolutionary path that eventually led to humans. It was a weird-looking beastie with a bag-like body and, for its size, a really big mouth.

University of Cambridge paleontologist Simon Conway Morris noted that humans, who appeared a relatively recent 200,000 years ago, have a series of “evolutionarily deeper ancestors” than monkeys and apes. That point is exemplified by the unique-looking creature called Saccorhytus, whose name means wrinkled sack.

“And is not beauty in the eye of the beholder?” Conway Morris asked.

Saccorhytus, measuring about four-hundredths of an inch (1 millimeter), appears to be the most primitive member of the broad animal group called deuterostomes.

This group includes vertebrates – fish, amphibians, reptiles, birds and mammals including people – as well as animals called echinoderms including starfish and sea urchins and obscure creatures called hemichordates including acorn worms.

Saccorhytus lived during the Cambrian Period, a time of exceptional evolutionary experimentation. The primitive biological traits possessed by Saccorhytus helped pave the way for the various deuterostomes including vertebrates. Fish, the vanguard of the vertebrates, appeared roughly 10 to 15 million years after Saccorhytus.

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