Minn. man draws link between sunshine, birth

Published 11:44 am Saturday, January 1, 2011

DILWORTH (AP) — Since first seeing a 1972 photograph of Earth taken on the final Apollo mission, an iconic shot of the planet partially shrouded in white puffs, David Cummings had often wondered what effect clouds have on humans.

“People seem to be happier when it’s sunny,” said Cummings, a Dilworth 74-year-old retiree. “That was the extent of it.”

Other than a pamphlet he released in 1983 on clouds and evolution, his interest remained at bay until he retired from a management job at Blue Cross Blue Shield in 1996.

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Since then, without any academic affiliation, he has authored six peer-reviewed journal articles connecting exposure to sunny days to seasonal spikes in births. His latest scientific article, published this fall, was the first to use North Dakota data to argue there’s a link.

As Cummings did when analyzing data from other points around the globe, he found that the month with the most sunshine — that’s September in North Dakota — corresponded with later increases in the birth rate.

North Dakota’s annual baby-bump occurs in August. Yes, that’s 11 months after September’s sun, but Cummings said the birth spike correlated with the brightest light exposure is two or three months longer than the nine-month length of a pregnancy.

Cummings can’t explain the lag, though he said it is longer in colder climes. Nor can he pinpoint why more sun eventually means a busier maternity ward. It could be that more sunshine simply encourages more sex, or vitamin D may play a role, he said.

Whatever the reasons, his findings are consistent.

“It’s legitimate science because you can disprove it. This is something a high school science class could disprove,” he said.

The connection between exposure to sun and birth seasonality could answer the vexing question of why the phenomenon — peaks in births at regular annual intervals — is seen in nearly all human societies, what Cummings calls a “200-year mystery.”

It also suggests the best months to try to conceive a child and shows how people are affected by the sun, Cummings said.

“To me, this is enough to really blow your mind,” he said. “It tells us something important about the human condition.”

Cummings said that while his theory explains part of the reason for birth seasonality, it can’t explain it all. It is probably influenced by a number of other factors.

However, he does think his work shows exposure to sunshine is the primary cause. In the North Dakota portion of his study, for example, he estimates that exposure to bright light is accounting for 65 percent of the birth-peak effect.

It’s rare for independent researchers to be published in peer-reviewed scientific journals, likely ensuring his articles get an intense review before they are published, Cummings said.

“To their credit, they’ve never said that,” he said of the journal editors he has encountered.

Peter Ellison is a professor of anthropology and human evolutionary biology at Harvard University and editor of the American Journal of Human Biology, a journal that’s published Cummings’ work.

Ellison said in an e-mail that he remains “agnostic” on Cummings’ theory, but reviewers for the journal “thought it was worth publishing, as it does fall in line with a contemporary line of research.”

As for Cummings’ wife of 50 years, Pat, she’s pleased her husband found something rewarding to work on in his retirement. She has also been impressed by the resilience he has shown in sticking with it.

He typically works on his articles for a few hours at night and only when the couple isn’t traveling so his research isn’t too obtrusive for the couple.

That doesn’t mean she never ribs him for it.

“When I get irritated, I call him the mad scientist,” Pat Cummings said.