Death by Cruise Ship, Lithium, and Suicide

Imagine that the Journal of Hypochondriacal Cardiology reported that the incidence of fatal strokes aboard cruise ships was five times the national average.  Should we conclude that the boat trips were killing passengers—and insist that Washington ban cruise ships?  Certainly not. Further investigation would probably reveal that the seafarers were comparatively old, and that they were not stroking out in greater numbers than were landlubbers of the same age.  The ships did not cause the deaths anymore than hospice centers kill people. Wherever old people congregate, one can expect deaths to be more prevalent than at places where younger people gather.


Mistaking correlation (ships and strokes) for causation (ships cause strokes) is an error in reasoning.  Jenny Listman, an anthropological geneticist at Yale, believes that the proponents of our first dangerous idea, Drug Our Drinking Water, are making the same kind of error. Bioethicist Jacob Appel cited two studies showing that the suicide rate was dramatically lower in places where the level of lithium in the water supply was naturally higher. In lower lithium areas in one of the studies, a third more people killed themselves.  And so Appel concluded that Washington, in the interest of saving 13,000 lives across the country, should perhaps spike all of our drinking water with lithium. 

Listman reviewed the two studies that Appel cited, and found methodological problems with the research. (You can read Listman's full analysis in the comment stream here.) She also cited work showing that in areas of high rainwater, lithium levels in drinking water were lower—presumably rain dilutes the lithium—and that suicide rates were higher in areas with heavy rain and lower where it's sunny.  In other words, it may be bad weather—not lithium—that's causally related to suicide.  Rather than drugging our drinking water, Washington might try to serve up a little more sunshine.

"Appel is an ethicist," Listman emailed me later, "and so is most concerned with the moral argument, and I was thinking after I posted my comment that I am entirely concerned with the scientific argument and was wondering if that means I'm insensitive. But I figure that there is no need to spend my energy on the moral argument if the science is invalid, and I can worry about the moral argument when it is relevant. It's also worth noting that I work in a psychiatric genetics lab group so I'm aware of the toll of mental illness on individuals as well as society."

When contacted by Big Think, Jacob Appel said he was "glad to respond to Jenny's thoughtful observations":

"As an ethicist, I am far more concerned with the morality of including beneficial additives to the drinking water than the specific benefits of any particular additive.  Whether or not lithium will prove beneficial, and whether the benefits, if they pan out, justify the cost, is an important question that should be explored further by epidemiologists and public health experts.  If it turns out that lithium does not indeed provide tangible benefits, then there would certainly be no purpose in adding it to the drinking water or consuming it in any other way.  Bioethicist Julian Savulescu has made a intriguing argument elsewhere that cognitive enhancement may be the next benefit provided by fluoride-like water treatments, another area certainly worth exploration.  So I am not wedded to lithium, per se, so much as the principle that using the drinking water to enhance public health is an idea that should be explored further and with an open mind.  I would also note that, if those who fear that trace amounts of drinking water were dangerous followed through on their arguments, they would campaign to have lithium removed from the water supply where it already naturally occurs."

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New fossils suggest human ancestors evolved in Europe, not Africa

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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.