On April 14th, 2015 we learned about

European genes assembled by a need for vitamin D

When humans moved into Europe 40,000 years ago, it’s assumed they arrived with dark skin. It’s also been assumed that they quickly started selecting for lighter skin in their new, Northern climate. Then, the thinking continued, after figuring out farming, this population started propagating genes for lactose tolerance, taking advantage of milk from the newly domesticated livestock. But DNA studies of European populations have been unraveling this tidy little story, revealing a more complicated and more recent timeline.

The genes researchers were looking for were those involved in a few different, and apparently discrete, traits. These included the LCT gene allowing the digestion of sugars in milk, SLC24A5 and SLC45A2, leading to pale skin, and HERC2/OCA2, which is the source of blue eyes, as well as possibly influencing lighter hair and skin pigmentation. And while it could have been possible to have all of these genetic changes sweep newly-settled Europeans all together, they seem to have come in multiple waves of influence from multiple sources.

Eating cheese and milk a fresher concept than previously understood

The new timeline starts with hunter-gatherers 8000 years ago, who were confirmed to not carry the LCT gene allowing lactose tolerance. This genetic variation wouldn’t take root until 2200 BCE, 5000 years after Europeans had been practicing agriculture. Two waves of immigrants that did bring many farming practices also lacked the gene upon arrival, indicating it may have developed in Europe. The advantage of consuming dairy went beyond gaining another source of calories- vitamin D was relatively scarce in Europe compared to humans’ original habitat further south, and milk products would have helped compensate for the loss of sunlight.

Soaking up any available sun

The need for vitamin D likely drove the propagation of genes for pale skin as well. Darker skin blocks more ultraviolet light than lighter skin, which, when less sunlight is available at higher latitudes, leads to a drop in the body’s synthesis of vitamin D. So while Southern Europeans were had dark skin until at least 5800 years ago, populations in the north were found to carry genes for lighter skin and lighter eyes as far back as 7700 years ago. It wasn’t until farmers from the Near East, who also had genes for lighter skin, immigrated to Europe that these variations started to spread across the whole continent.

So the piecemeal story of both diary consumption and pale pigments may still have the one common thread— vitamin D. While vitamin D does play a role in our immune system, other genes for immune response didn’t seem to be pressured or propagated in the European population in the same way, even with the introduction of farming, animal husbandry, and new populations. All that mattered was making up for the loss of sunshine.

Source: How Europeans evolved white skin by Ann Gibbons, Science

On April 6th, 2015 we learned about

Seeing snakes was a top primate priority

Humans have notably good vision, especially among mammals. We see more colors and in higher resolution than the average dog or deer. And of course, our forward-facing eyes give us depth perception, similar to hunters like lions or owls. But we’re not chasing down much colorful prey with our bare hands, so what was the initial advantage for our primate ancestors to develop better vision?

Seeing prey or predators

The answer may not be what we were after, but what may have been after us. Multiple forms of evidence have been gathered that point to the need to avoid venomous snakes as a reason for our visual abilities, the most recent of which was a survey of snakes in chimpanzee country.

Researchers spent four years documenting snakes they encountered in areas where chimpanzees live. 64% of the snake species encountered were venomous, and the researchers generally sense that their encounter rate is likely lower than what our ancestors would have faced. They also noted that their detection rate is likely lower than a group of chimps working together, just based on the number of eyes keeping watch alone.

More evidence for the Snake Detection Theory

The Snake-Detection Theory (SDT) is built on more a lot of snakes though. Championed by anthropologist Lynne Isbell, the number of snakes in an area has been compared to the visual abilities of local primates, and they show a strong correlation. For instance, lemurs on Madagascar have the worst primate vision, but they have no venomous snakes to contend with.

Primate brains provide more evidence for SDT. Neuroscientists looked at macaque monkeys, and found that their brain registered visual stimulus from snakes faster than to any other objects. What’s more, that recognition was even faster if the snake was seen in a coiled, threatening posture.

All together, this suggests that the need to quickly see the shape and color of a snake among the forest leaves, and then recognize it as a threat, was a significant advantage for our primate ancestors. Our visual capabilities have obviously bestowed other benefits since then, but a fear of serpents may have kicked it all off.


My kindergartner says: Another experiment should be done with the  macaque monkeys, wherein they are placed in a “tent” with pictures or projections of a real jungle inside it. An image or video of a snake would be hidden somewhere in that virtual jungle, and the test would be to see how quickly the monkey could pick the snake out of that scene. And there would be “a window so we could watch the monkey” of course.

Source: We May Have Snakes To Thank For Our Acute Vision by Barbara J. King, Cosmos & Culture

On March 3rd, 2015 we learned about

The History of Lucky Dolls

March 3rd is Hinamatsuri in Japan, also known as Girl Day and Doll Day. Since the Heian period approximately 1200 years ago, people have created and displayed dolls to ensure good luck.

The dolls represent the Emperor, Empress, and their attending court. They are traditionally set upon rows of platforms covered in red carpet, with a set hierarchy for each tier. While setup can begin in February, the dolls are to be taken down by March 4th to avoid causing a late marriage for one’s daughter.

Earlier versions of Hinamatsuri show more connections to Shinto beliefs, with the dolls being created out of straw in order to contain bad spirits people wanted to drive away. The straw dolls were floated down the river on a boat, putting distance between their owners and the spirits. After fisherman complained about catching too many dolls in their nets, the ritual was moved to the sea side, where they could be recaptured en mass, and then disposed of in a fire.

Source: Hinamatsuri, Wikipedia