Aging, hominid ears, whales and more reader feedback

How hominids heard

Ancient South African hominids that lived between 2.5 million and 1.5 million years ago could have heard high-frequency consonants better than either chimps or modern humans. An ability to hear, and presumably make, these sounds might have made these species more competitive, Bruce Bower wrote in “Ancient hominid ears were tuned to high frequencies” (SN: 10/31/15, p. 17).

Such communications would not have required a language like that of modern humans, Bower wrote, but simply vowel and consonant sounds with shared meanings. Reader Mike Kobrick wanted to know what distinguishes a language. “If vowel and consonant sounds with shared meanings isn’t language, then what is?” he asked in an e-mail.

There’s a big difference between sound combinations with shared meanings, such as warning or mating calls, and a grammatical language with words that can be combined in a multitude of ways to express all sorts of ideas, Bower says. Scientists consider the use of a complex grammatical structure a trait that separates humans from other animals. For decades, scientists have been debating how early hominids communicated. Unfortunately language, like social behavior, doesn’t fossilize, Bower notes.

A way to stop aging?

Scientists discovered that the GATA4 protein acts like a biochemical switch and forces cells to stop growing and dividing, Sarah Schwartz reported in “Protein buildup triggers cellular aging” (SN: 10/31/15, p. 7).

The researchers also found that GATA4 accumulates with age. This caused online commenter Mike G to wonder, “If they find a way to get rid of GATA4 proteins, will that end aging?”

Getting rid of GATA4 altogether would definitely be problematic. The protein has a lot of other functions in the body, including helping organs develop, says geriatrician James Kirkland of the Mayo Clinic in Rochester, Minn.

For example, says geneticist Stephen Elledge of Harvard Medical School, “you can’t make your heart without it, and testes are inactive if you don’t have GATA4.” He says that turning off the genes that make GATA4 isn’t necessarily the answer to combatting cell senescence or aging. However, it might be possible to find a way to reverse the “switch” that GATA4 flips that causes cells to halt growth. Or it could be useful to target the protein only in adults, after new tissues finish developing. For now, the researchers say there’s a lot more to learn about exactly how the protein functions and how the genes that control it work.

Bird breath

Birds aren’t the only creatures to breathe with one-way airflow, Susan Milius revealed in “Chasing breath” (SN: 10/31/15, p. 22). Alligators and some lizards do, too, which offers tantalizing clues about the evolution of lungs in these groups.

Reader Patrick McMonagle speculated about whether the mechanisms of one-way airflow allow birds to breathe more efficiently with less oxygen. Millions of years ago, when Earth’s atmospheric oxygen levels would have been much lower than today’s, “such a function could add enough evolutionary advantage” that creatures using one-way airflow had a competitive edge, he posited in an e-mail.

“It does seem like the big advantage of one-way flow in the bird lung exists when they are breathing lowered oxygen,” agrees University of Utah researcher Colleen Farmer, who’s studying one-way air flow in reptile lungs. She points out that during the Mesozoic era, which started about 251 million years ago, ancestors of birds and crocodilians diversified into a great variety of forms. Oxygen was less concentrated in the atmosphere, she says. Unidirectional air flow may have been one of the features that gave these ancient reptiles an advantage over mammals during that time.