We take scientific rigor very seriously at Clue, and as we grow, so does our scientific body of knowledge and curiosity. And that’s why we’re so proud to announce that Dr. Virginia J. Vitzthum from the Kinsey Institute will be joining our science team.
Dr. Vitzthum is an evolutionary biologist whose work focuses on women’s reproductive function and how it differs between individuals and across populations around the world.
During the mid 1990s, Dr. Vitzthum directed Project REPA, a longitudinal study of reproduction and hormone levels in highland Bolivian women. This study hoped to gain insight into a long standing puzzle: why is it that women in industrialized countries who undertake intensive athletic training or other exercise programs usually stop ovulating, yet women in non-industrialized countries often have many children despite regularly engaging in arduous physical labor?
Vitzthum and her colleagues found that despite high altitude, heavy physical labor and consuming an average of only 1800 calories per day, the Bolivian women ovulated, conceived and birthed healthy children while having reproductive hormone levels only about 2/3 of those considered typical in the US.
Dr. Vitzthum explains these and other observations in terms of a “Flexible Response” model in which humans have evolved to adjust reproductive functioning to the ambient environment. Evolution rewards successful reproduction, but pregnancy and childbirth are very risky for the mother if conditions (nutrition, workload, health) are poor. Using the analogy of a poker game, Vitzthum explains that that if you’re unlikely to ever get any good hands, then it’s worth betting on even mediocre hands. For women, this means that if you’ve lived all your life in an arduous environment then that’s probably what you can expect for the future, so your body reacts by ovulating and potentially conceiving despite the arduous conditions.
It’s long been known that some 80% of all human conceptions are lost within the first 6 weeks of pregnancy. In Project REPA, Dr. Vitzthum and her colleagues found that early pregnancy losses were much more frequent during the planting season, when physical labor is high and food supplies are scarce. This proves that many early pregnancy losses aren’t caused by genetic factors (which wouldn’t vary much from one season to another). Instead, Vitzthum suggests an evolutionary strategy of “tentative reproduction” where the body ovulates (and potentially conceives) even if conditions seem marginal for a successful pregnancy, than continues the pregnancy only if conditions improve.
In 2006 Dr. Vitzthum studied nomadic herders in central Asia, whose diet has a calorie intake almost as low as Bolivians, yet very high levels of animal fat. She found that these women have very high reproductive hormone levels, suggesting that dietary fat may be more important than overall caloric intake in determining hormone levels.
In 2007-8 Dr. Vitzthum spent a year at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, comparing hormone levels in women who grew up in the former East versus West Germany. These populations were genetically similar but had quite different diet and activity patterns prior to German reunification. She found that despite growing up in “poorer” environments, the former East Germans had higher hormone levels than the former West Germans. The causes of this difference (which is opposite to the usual pattern in international comparisons, where women who grow up in poorer environments have lower hormone levels) are uncertain but may be related to the high animal fat diet of east Germans.
Dr. Vitzthum is currently studying women in Iceland to explore how their reproductive and other hormone levels are affected by the extreme seasonality of very little sunlight in the arctic winter versus nearly continuous sunlight in the arctic summer.
High levels of reproductive hormones are a major risk factor for breast cancer and other diseases. Dr. Vitzthum has found that throughout the world, there’s far more woman-to-woman variation in these hormone levels than is commonly assumed. Understanding this variation could help guide medical monitoring and cancer screening to better target those most at risk. The large variation in hormone levels also means that “one size fits all” hormonal contraceptive doses may be unsuitable for many women (those with lower natural hormone levels), leading to serious side effects.
Dr. Vitzthum is a Fellow of the American Association for the Advancement of Science. She is currently a Professor in the Department of Anthropology, a Senior Research Scientist at the Kinsey Institute, and Director of the Evolutionary Anthropology Laboratory, all at Indiana University in Bloomington.
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