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Readers react to mammoths, parasitic plants, and many more millions of years ago

Large mouths to feed

The oldest animal DNA that has been recovered comes from a mammoth that lived more than a million years ago, Erin García de Jesús reported in “Million-Year-Old Mammoth DNA Found” (SN: 13/03/21, p. 6).

Given that a modern elephant can consume hundreds of kilograms of plant food a day, it could eat the mammoth in the frozen tundra, reader Peter Nissenson he asked.

Researchers do not know for sure what the ancient animal may have eaten. But like other mammoths, its menu may include flowers and herbs (SN: 22/03/14, p. 13). Recent studies suggest that declining food sources contributed to the extinction of most mammoths about 10,000 years ago. García de Jesús of. "Just as the flowers are gone, so are the mammoths."

A wild escape

Genes escaped from modified cotton crops are disrupting the interactions of wild cotton with insects, causing irreversible ecological effects. Emiliano Rodríguez Mega reported in “Modified genes can harm wild cotton” (SN: 13/03/21, p. 10).

Reader Marc Sapir I wondered why the effects are irreversible if wild cotton plants with escaped genes struggled more to survive than those that didn’t.

Once genes escape, we can no longer control how they behave or where they are going, Rodriguez Mega of. That doesn’t necessarily mean that genes devastate wild cotton populations. But there is currently no way for scientists to rid those populations of genes.

Genes could disappear if they are selected by natural forces, Rodriguez Mega he says, but we don’t know that will happen. More studies are needed to understand the long-term effects that escaped genes could have on nature.

What does a plant do?

A parasitic plant, Sapria himalayana, has lost genes for stems, roots, and photosynthetic tissue to live within its hosts. Jake Buehler reported in “A parasitic plant lacks many genes” (SN: 13/03/21, p. 13).

Considering all that S. himalayana has lost, "is it still a plant?" reader Jeff Fisher he asked. Could it be something completely new?

Biologists group organisms based on their shared evolutionary history, so S. himalayana is still considered a plant, Buehler of. But taxonomists and other researchers have long debated when an organism deviates enough from its ancestral line to obtain a unique taxonomic rank. There is currently no standard that scientists use to determine these limits, Buehler of.

The researchers found that the parasite took a lot of DNA from its hosts, although much of it does not encode any genes, Buehler reported. Reader D.C. Randle it was questioned why the plant would bother to snatch this genetic material.

Some of the stolen DNA encodes genes. And those genes can be useful, Buehler of. Some are involved in parasite defense and stress responses, and another is critical in making pyrimidine, a key block of nucleic acids such as DNA.

Flying high

Sunlight-powered microflectors can fly in conditions such as high in the Earth's atmosphere. Emily Conover reported in “Small planes flying with light could shoot out of range of aircraft” (SN: 3/13/21, p. 5).

Reader William S. Darter I was wondering how scalable these microfliers could be.

"The lifting forces produced in this case are quite small, so the plane and its instruments have to be extremely light." Conover of. That makes the aircraft a scale challenge. "One idea would be to create arrays of microflectors connected by thin carbon fibers. That would allow microfliers to carry more massive payloads, albeit only in the gram range."


“Two new books seek the meaning of life” (SN: 27/03/21, p. 28) incorrectly stated that a person’s metabolism increases approximately 0.5 times their resting rate after eating. Metabolism increases up to about 1.5 times the resting rate.

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