Reuters Science News Summary

Following is a summary of current science news briefs.

Car-sized prehistoric South American turtle was built for battle

One of the largest turtles that ever lived prowled the lakes and rivers of northern South America from about 13 million years ago to 7 million years ago - and this car-sized freshwater beast was built for battle. Scientists said on Wednesday they have unearthed new fossils of the turtle, called Stupendemys geographicus, in Colombia's Tatacoa Desert and Venezuela's Urumaco region that for the first time provide a comprehensive understanding of the big reptile, which got up to 13 feet (4 meters) long and 1.25 tons in weight.

Oddly shaped celestial body Arrokoth sheds light on planet formation

A vaguely hourglass-shaped icy object called Arrokoth residing in the far reaches of the solar system - the most distant body ever explored by a spacecraft - is giving scientists intriguing clues about the formation of the planets including Earth. Scientists on Thursday offered the fullest description yet of the composition and origin of Arrokoth based on data from NASA's New Horizons spacecraft, which whizzed past it last year.

'Ghost' ancestors: African DNA study detects mysterious human species

Scientists examining the genomes of West Africans have detected signs that a mysterious extinct human species interbred with our own species tens of thousands of years ago in Africa, the latest evidence of humankind's complicated genetic ancestry. The study indicated that present-day West Africans trace a substantial proportion, some 2% to 19%, of their genetic ancestry to an extinct human species - what the researchers called a "ghost population."