Today in Science: Human ancestors nearly went extinct

September 6, 2023: A new translation of Newton's laws, human ancestors nearly didn't make it and autumn fog is filling up valleys in the Northeast.
Andrea Gawrylewski, Chief Newsletter Editor
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Bodies in Motion

A subtle mistranslation of Isaac Newton's first law of motion that flew under the radar for three centuries is giving new insight into the physicist/philosopher's intention. The common paraphrasing "objects in motion tend to stay in motion, and objects at rest tend to stay at rest," isn't quite a true representation of the original Latin, according to a new paper. Virginia Tech philosopher Daniel Hoek argues that the original wording in Latin of the first law would be better paraphrased: "Every change in a body's state of motion is due to impressed forces."

Why this matters: Throughout the centuries, many philosophers of science have interpreted Newton's original Latin phrasing to be about bodies that don't have any forces acting upon them (bodies at rest). But no body in the universe has zero forces acting upon it, so this has always been a bit puzzling. Einstein built his theory of general relativity on Newton's laws, and some have used the subtle mistranslation of Newton's words as evidence that Einstein and Newton disagreed, philosophically. 

What the experts say: Not only did Newton not intend to make a law about imaginary force-free bodies, says Robert DiSalle, a historian of the philosophy of physics at Western University in Ontario, but Newton's contemporaries didn't interpret him that way, either, which suggests that the misinterpretation is a relatively recent phenomenon.

Ancient Bottlenecks

Our human ancestors in Africa were pushed to the brink of extinction around 900,000 years ago, a new genetic analysis shows. The population of breeding individuals was reduced to just 1,280 (a reduction of about 98.7 percent of human ancestors!) and didn't expand again for another 117,000 years. This time period experienced drastic climate changes, including long periods of drought in Africa that might have wiped out some human ancestors and forced new human species to emerge. 

How this was discovered: Using newly-devised genomic tools, researchers reconstructed ancient population dynamics on the basis of genetic data from present-day humans. By constructing a complex family tree of genes, the team could examine the finer branches of the tree with greater precision, identifying significant evolutionary events. They eventually identified a time period about 800,000 to 1 million years ago when this near-extinction event took place.

What the experts say: The genetic bottleneck likely had a crucial impact on human genetic diversity, driving many important features of modern humans, such as brain size, says Ziqian Hao, a population geneticist at the Shandong First Medical University. He estimates that up to two-thirds of genetic diversity was lost. 
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IMAGE OF THE DAY
Credit: NOAA/NESDIS/STAR GOES-East - Geocolor Composite
Cool morning air settles in river valleys across parts of New York and Pennsylvania leading to the development of valley fog, seen as the jagged, vein-like clouds in this satellite image. This is a common phenomenon in fall as air temperatures cool overnight. 
We Homo sapiens were never a guaranteed thing. In our long story of evolution we've faced extinction multiple times. The new finding above reminded me of one of my favorite articles in the Scientific American archive, which details a period between 195,000 and 123,000 years ago when the human population plummeted and those who survived made a living by fishing and hunting on the coasts of Africa. 
Thanks for reading Today in Science. I'll see you tomorrow! 
—Andrea Gawrylewski, Chief Newsletter Editor
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