'Swallowing sperm' linked to lower risk of recurring miscarriage, researchers say

Don't get too excited, there is a catch to the study.

  • A new study finds a relationship between how often women gave their partners oral sex and the number of miscarriages they'd endured.
  • While it demonstrates correlation, the study does not prove causation.
  • The study will undoubtedly be the catalyst for further studies into this area.

A new study, published in Journal of Reproductive Immunology on March 27, suggests that woman who more frequently gave their partners oral sex, and swallowed the semen, were less likely to suffer recurring miscarriages.

Wait; what?

In the study, Dutch researchers compared the habits of 97 woman who have suffered recurrent miscarriage, defined as the loss of three or more consecutive pregnancies, to 137 women who did not. It was found that the woman who did not endure recurring miscarriages were performing markedly more oral sex on their partners than the members of the former group.

Of the women with recurring miscarriages, a little more than half reported giving oral sex. Nearly 75 percent of the other group reported doing so.

Now, this is all just correlation right now, and we all know that correlation does not prove causation. The scientists have yet to identify a mechanism that relates giving oral sex and having fewer miscarriages. It also relies entirely on self-reporting by a small number of test subjects.

At this point we don't know if the results aren't caused by other factors — suppose that woman who enjoy giving oral sex are just somehow inclined to have fewer miscarriages, for example. However, this study could be the basis for further investigation into the issue that does find something more tangible.

The authors of the study have speculated on what that mechanism might be. One idea is that exposure to the genetic material of their partners might be giving their immune system time to recognize it and reduce the chance it will see a fetus as foreign if it includes the same DNA. As they mentioned in their study, this notion isn't without precedent:

"A well-known route to induce immune tolerance is via oral exposure, possibly because the gut has the most adequate absorption in the absence of an inflammatory environment. In transplantation models of rats, oral administration of MHC molecules diminishes the occurrence of allograft rejection. In addition, Clark et al showed that direct seminal plasma antigen presentation to a mouse model of NK-cell mediated recurrent miscarriage may prevent the rejection of embryos. Koelman et al hypothesized that a potent way of inducing tolerance towards paternal HLA antigens of the fetus in pregnancy would be exposure of these antigens to oral mucosa. To support this theory, they showed that both oral sex and swallowing sperm reduced the incidence of preeclampsia."

The above excerpt references several other studies, including one that showed a connection between swallowing semen and a reduced rate of preeclampsia in expecting mothers.

The researchers conclude, "[Oral] exposure to seminal fluid seems to induce maternal tolerance to paternal antigens and therefore influence pregnancy outcome in a positive way."

The maternal immune system

Strange as it is to think, in a way a fetus is like a foreign object in the mother's body which the immune system would have an interest in. While the womb is supposed to be an immunologically privileged area, some studies have suggested that unexplainable miscarriages could be caused by an immune response to the fetus. RH disease and preeclampsia are examples of less severe reactions to an improper immune response.

While the idea of more oral sex as a practical solution to the problem of recurring miscarriage will undoubtedly interest quite a few people, the jury is still out.

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New fossils suggest human ancestors evolved in Europe, not Africa

Experts argue the jaws of an ancient European ape reveal a key human ancestor.

Surprising Science
  • The jaw bones of an 8-million-year-old ape were discovered at Nikiti, Greece, in the '90s.
  • Researchers speculate it could be a previously unknown species and one of humanity's earliest evolutionary ancestors.
  • These fossils may change how we view the evolution of our species.

Homo sapiens have been on earth for 200,000 years — give or take a few ten-thousand-year stretches. Much of that time is shrouded in the fog of prehistory. What we do know has been pieced together by deciphering the fossil record through the principles of evolutionary theory. Yet new discoveries contain the potential to refashion that knowledge and lead scientists to new, previously unconsidered conclusions.

A set of 8-million-year-old teeth may have done just that. Researchers recently inspected the upper and lower jaw of an ancient European ape. Their conclusions suggest that humanity's forebearers may have arisen in Europe before migrating to Africa, potentially upending a scientific consensus that has stood since Darwin's day.

Rethinking humanity's origin story

The frontispiece of Thomas Huxley's Evidence as to Man's Place in Nature (1863) sketched by natural history artist Benjamin Waterhouse Hawkins. (Photo: Wikimedia Commons)

As reported in New Scientist, the 8- to 9-million-year-old hominin jaw bones were found at Nikiti, northern Greece, in the '90s. Scientists originally pegged the chompers as belonging to a member of Ouranopithecus, an genus of extinct Eurasian ape.

David Begun, an anthropologist at the University of Toronto, and his team recently reexamined the jaw bones. They argue that the original identification was incorrect. Based on the fossil's hominin-like canines and premolar roots, they identify that the ape belongs to a previously unknown proto-hominin.

The researchers hypothesize that these proto-hominins were the evolutionary ancestors of another European great ape Graecopithecus, which the same team tentatively identified as an early hominin in 2017. Graecopithecus lived in south-east Europe 7.2 million years ago. If the premise is correct, these hominins would have migrated to Africa 7 million years ago, after undergoing much of their evolutionary development in Europe.

Begun points out that south-east Europe was once occupied by the ancestors of animals like the giraffe and rhino, too. "It's widely agreed that this was the found fauna of most of what we see in Africa today," he told New Scientists. "If the antelopes and giraffes could get into Africa 7 million years ago, why not the apes?"

He recently outlined this idea at a conference of the American Association of Physical Anthropologists.

It's worth noting that Begun has made similar hypotheses before. Writing for the Journal of Human Evolution in 2002, Begun and Elmar Heizmann of the Natural history Museum of Stuttgart discussed a great ape fossil found in Germany that they argued could be the ancestor (broadly speaking) of all living great apes and humans.

"Found in Germany 20 years ago, this specimen is about 16.5 million years old, some 1.5 million years older than similar species from East Africa," Begun said in a statement then. "It suggests that the great ape and human lineage first appeared in Eurasia and not Africa."

Migrating out of Africa

In the Descent of Man, Charles Darwin proposed that hominins descended out of Africa. Considering the relatively few fossils available at the time, it is a testament to Darwin's astuteness that his hypothesis remains the leading theory.

Since Darwin's time, we have unearthed many more fossils and discovered new evidence in genetics. As such, our African-origin story has undergone many updates and revisions since 1871. Today, it has splintered into two theories: the "out of Africa" theory and the "multi-regional" theory.

The out of Africa theory suggests that the cradle of all humanity was Africa. Homo sapiens evolved exclusively and recently on that continent. At some point in prehistory, our ancestors migrated from Africa to Eurasia and replaced other subspecies of the genus Homo, such as Neanderthals. This is the dominant theory among scientists, and current evidence seems to support it best — though, say that in some circles and be prepared for a late-night debate that goes well past last call.

The multi-regional theory suggests that humans evolved in parallel across various regions. According to this model, the hominins Homo erectus left Africa to settle across Eurasia and (maybe) Australia. These disparate populations eventually evolved into modern humans thanks to a helping dollop of gene flow.

Of course, there are the broad strokes of very nuanced models, and we're leaving a lot of discussion out. There is, for example, a debate as to whether African Homo erectus fossils should be considered alongside Asian ones or should be labeled as a different subspecies, Homo ergaster.

Proponents of the out-of-Africa model aren't sure whether non-African humans descended from a single migration out of Africa or at least two major waves of migration followed by a lot of interbreeding.

Did we head east or south of Eden?

Not all anthropologists agree with Begun and his team's conclusions. As noted by New Scientist, it is possible that the Nikiti ape is not related to hominins at all. It may have evolved similar features independently, developing teeth to eat similar foods or chew in a similar manner as early hominins.

Ultimately, Nikiti ape alone doesn't offer enough evidence to upend the out of Africa model, which is supported by a more robust fossil record and DNA evidence. But additional evidence may be uncovered to lend further credence to Begun's hypothesis or lead us to yet unconsidered ideas about humanity's evolution.