June 27, 2024: Life on Earth made this planet what it is, not the other way round. Plus, what humans really evolved to eat and the adaptability of great tits (the birds). —Andrea Gawrylewski, Chief Newsletter Editor | | | Earth as we know it would not exist without life. The planetary processes that we typically think of as inanimate (nutrient cycles, geologic formations) are actually infused with and powered by life, argues Ferris Jabr, author of the new book Becoming Earth: How Our Planet Came to Life. Life created the oxygen that we breathe and the ozone layer that protects us from the sun. It turned barren rock into fertile soil. It carves caves, forges new mineral species, and may even have helped create the continents. One of Jabr's favorite examples of this transformative power happens in the Amazon rainforest, where plants, animals, fungi and microbes generate half of the rainfall that sustains them, making the ecosystem a sort of "garden that waters itself," he writes.
Why this is interesting: Scientists have long accepted that the Earth shapes life, but only recently have they begun to accept life's active role in shaping Earth. In the 1970s, chemist James Lovelock formulated the Gaia hypothesis based on this insight, and it received harsh criticism from the scientific community. But decades later, "a huge amount of evidence has shown that some of the core tenets of what Lovelock was saying are indeed true," Jabr says.
Why this matters: Most life-forms have transformed our planet gradually, developing rhythms and processes that maintain Earth's equilibrium. But humans, "in a geological blink, have massively perturbed those rhythms. I think that clarifies for us exactly what our responsibility is, compared with all other life-forms," Jabr says. "There's something empowering about this framework. We have both this privilege and responsibility, not just to each other and to other life-forms but to the larger living system of which we are a part." --Allison Parshall, news editor | | | TikTok, Instagram and YouTube are full of popular personalities peddling meat-centric diets. These diets shun ultraprocessed foods (potato chips, breakfast cereals, packaged breads, sodas). They also restrict fruits and discourage vegetables, which they claim are loaded with chemicals that are toxic to humans. These meat lovers claim their regimens are ideal for humans because they are "ancestral," made up of the foods our ancient predecessors ate. Yes, meat-eating came about several million years ago in our evolutionary history, but according to fossils, ancient DNA and tooth remains, humans are decidedly omnivores.
The evidence: Researchers analyzed the tartar preserved in the stained teeth of two Australopithecus sediba individuals from South Africa that lived two million years ago. In that tartar they found microscopic bits of silica from plants, including bark, leaves, sedges and grasses. The evolution of hominin tooth morphology over time shows that australopiths had big, flat teeth with thick enamel—traits specialized for crushing hard foods such as seeds. Even Neanderthals consumed plants–traces of legumes, dates and wild barley show up in the tartar on their fossilized teeth. Alongside remains of butchered animal bones at sites linked to Homo erectus populations, scientists found other tools that exhibit wear patterns consistent with chopping herbaceous plants and root vegetables.
What the experts say: "When I think about changes in diet over time, I don't think the change was linear," says Briana Pobiner, a paleoanthropologist at the Smithsonian National Museum of Natural History, of hominins' dietary evolution. In many ways, the changes have been more about broadening the diet rather than progressing from vegetarian to meat eater, she explains. "Humans are omnivores," she says. "We've always been omnivores." | | | Sensory nerve cells called Krause corpuscles are denser on the clitoris of female mice (left) than on the penis of male mice (right). Lijun Qi/Michael Iskols/David Ginty | | | • Specific nerve cells on the penis and clitoris of mice can detect low-frequency vibrations in the range of 40–80 hertz and then become activated, according to new research. | 3 min read | | | • Older people are increasingly becoming the targets of fraud. Here's how to stay safe and what to do if you think you've been scammed. | 6 min read | | | • The great tits are some of the most recognizable birds in Europe and Asia. They evolved in deciduous forests but survive remarkably well in urban environments, which could "offers some lessons on how we can better get along with not just great tits, but our other urban animal neighbors," writes Anders Brodin, a professor in ecology at Lund University, Sweden. "Considering the cognitive ability in a small bird such as the great tit, there should be room for much reflection when we think about the confined spaces where we keep animals that we consider to be even more cognitively advanced, in zoos," he says. | 5 min read | | | Great Tit (Parus major) adult and Blue Tit (Parus caeruleus) adult foraging for insects on crabapple fruit Suffolk England. FLPA/Alamy Stock Photo | | | The lives of animals are often an afterthought when planning human urban or suburban lives. Is there a way to be better neighbors to the creatures we share this planet with? In the July/August issue of Scientific American, author Tove Danovich reviews a new book, Meet the Neighbors, by Brandon Keim, who suggests ways for humans to treat animal neighbors with more fairness. "What if we considered animals as stakeholders that should be heard before harvesting timber from a forest, using pesticides in agriculture, or removing 'nuisance' animals that aren't causing damage or harm?" Danovich asks. | This newsletter is for you! Reach out any time with suggestions for how to improve it: newsletters@sciam.com. Thanks for reading. | —Andrea Gawrylewski, Chief Newsletter Editor | | Subscribe to this and all of our newsletters . | | | | Scientific American
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