These results do not square with expert predictions_其他

These results do not square with expert predictions

As we dramatically reduce birthrates across the globe, where there will soon be more of us over age 60 than under 14, it is the reverse that must begin to animate our thinking: What does a working life look like in the 21st century when there are two decades beyond 20th century traditional retirement age?

- Social Security Must Confront Its Own Mortality, BusinessInsider.com, August 13, 2017.

3. After climbing a tree in the middle of the Yukon forest, I looked into a squirrel’s nest and found a pup that clearly did not belong there. It was older and larger than the others in the litter. My research team and I collected DNA from the whole litter and later, back at the genetics laboratory, the mystery was solved: We determined that the larger pup had been adopted by an older sister after its mother had been killed by a predator.

Altruistic behaviors can take on many forms, even among non-human animals. For example, they may warn neighbors of nearby predators or quell a dispute between two individuals fighting one another. But perhaps the most altruistic behavior of all is to care for an orphaned offspring as though it were one of your own.

I am by no means the first researcher to discover a case of adoption in the wild. It has been observed in over 60 different species of mammals, from mice to elephants to whales. Nevertheless, adoptions in the wild are quite rare. What can explain these seemingly altruistic acts?