Natural selection is weeding Alzheimer’s and asthma out of gene pool

ALZHEIMER’S disease, high cholesterol and asthma are being “weeded out” of the human gene pool by natural selection, the first major study of its kind has revealed.

Analysis of the genetic blueprints of 150,000 Britons and 60,000 Americans found the variations associated with the illnesses had noticeably declined in the space of just two generations.

Researchers believe men with Alzheimer’s tend to have fewer children, and that both men and women with the condition are less able to look after their grandchildren. This affects survival and limits the proliferation of those faulty genes, while genetic traits associated with good health are more likely to be passed on, becoming increasingly common in the human gene pool.

It means that, in theory, devastating illnesses such as Alzheimer’s could be bred out of the human species within a few thousand years. The research team at Cambridge and Columbia Universities said their study, published in the journal PLOS Biology, showed how the genomic “revolution” was enabling them to see Darwinian evolutionary theory play out in practice.

“It’s a subtle signal, but we find genetic evidence that natural selection is happening in modern human populations,” said Joseph Pickrell, an evolutionary geneticist at Columbia, and one of the study’s authors.

The study also found that people genetically predisposed to delayed puberty and child-bearing lived longer. A one-year puberty delay lowered the death rate by three to four per cent, while a one-year child-bearing delay lowered the death rate by six per cent.