Science and Religion Blah Blah Blah









The evolution of human facial diversity

Signalling individual identity is critical in many aspects of human social interaction (click for video!).

We all rely on our ability to recognize other people’s faces to get along in the world. Most people don’t think too hard about this, it’s so fundamental to our existence. But it turns out that in order to stand out in the crowd, you need to be, well different. A recent study shows that human faces are in fact, much more different from one another than other traits, and suggests that this high facial diversity has evolved specifically to signal individual identity. It’s a pretty interesting story, and I look forward to digging into the details.

Check out this NatGeo piece on the work, and the original publication (paywalled).

Literature Cited:
Sheehan, Michael J., and Michael W. Nachman. “Morphological and population genomic evidence that human faces have evolved to signal individual identity.” Nature Communications 5 (2014).

Random Natural History: Ebola

through a glass, darkly



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BAH! Fest – 2014


Random Natural History: Salvin’s Albatross

Salvin's Albatross (Thalassarche salvini)

On Saturday, a Salvin’s Albatross was sighted by birdwatchers on a tour just off the coast of Northern California. This is an extremely rare occurrence. How rare? A bird-blogger who was on the tour writes:

Salvin’s Albatross are well-known for their habit of avoiding the northern hemisphere. It is so rare that I can’t really wrap my mind around it. It’s a bird I don’t look for when I am looking for rare birds. It is the rarest seabird, geographically speaking, that I have ever seen.

So, what is a Salvin’s albatross? For that matter, what are albatrosses? And what makes this such an unusual sighting?

Albatrosses are birds in the family Diomedeidae. They are large, long-lived birds that spend virtually their entire lives at sea. There are way too many cool aspects of albatross biology to cover here, but here are two to chew on:

1) They use dynamic soaring and slope soaring to travel thousands of miles with hardly a flap of their wings. In fact, they are so large, and so well adapted for gliding flight they aren’t very well equipped for typical flapping flight.

2) They have elaborate courtship rituals that play out over years, and result in life-long pair bonds. For some species, “life-long” means over 50 years. Below are Waved Albatross (Phoebastria irrorata) on the Galapagos Islands.

So what’s Salvin’s Albatross, then? Thalassarche salvini is a southern hemisphere albatross species. It’s part of a complex of four species that used to be considered one. They’ve since been split, and what’s now recognized as Salvin’s breeds primarily on two remote island complexes near New Zealand: The Bounty Islands and the Western Chain of Snares Islands, although a handful of breeding pairs have been recorded on scattered islands thousands of miles distant (but still in high latitudes of the Southern Hemisphere).

While foraging, Salvin’s Albatrosses wander the southern oceans. Their core range is from Australia to western South America, but they’ve been recorded in the southern Indian Ocean as well. The key to their rarity in northern oceans is probably lies in the trade winds. Because (as I mentioned above), albatrosses are so exquisitely adapted for gliding flight, so adept at using wind and waves to stay aloft, and not very good flapping fliers, they are also dependent on wind and waves being consistently available to get around. This means the horse latitudes, or the doldrums (bands of low wind encircling the earth at around 35 degrees latitude) probably form quite effective barriers for them.

So this individual spotted off the coast of California is a long way from home, and could probably spin an interesting yarn about just how it ended up here. How long it will stay in the northern Pacific, or if it will ever make the journey back home, we’ll probably never know.

Random Natural History: Valley Oaks and their Galls.

Ok, time for a short bit of natural history. I live in the Sacramento Valley in northern California. The dominant tree species (outside of urban areas) seems to be the Valley Oak (Quercus lobata). Now, there aren’t a whole lot of trees in the valley, so it’s pretty lucky that Valley Oaks are fairly spectacular.

Valley oak (Quercus lobata) on Joseph D Grant County Park Canada de Pala Trail

They are also little ecosystems unto themselves. The first thing most people notice about them are oak apple galls, so called because they bear a disturbing resemblance to (rotting) apples.

"Oak apple" galls of California Gall Wasps (Andricus quercuscalifornicus, Cynipidae, Hymenoptera) on Valley Oak (Quercus lobata, Fagaceae)

Trees can often be so laden with them that they actually look like cultivated apple trees. The galls are woody, though, not squishy like actual apples. What is a gall, you ask? Good question. A gall is essentially a plant tumor. In many cases (as here) galls are caused by insect parasites. An adult insect lays eggs in the tissue of a plant, and those eggs release hormones that induce the plant to form the gall. Galls can provide food and shelter for their hosts until they are ready to mate and lay new eggs. Galls can be quite complicated structures, the result of parasites evolving very refined control over their hosts over time. As a result, galling insects can frequently be identified by their galls alone. Oak apple galls are caused by a wasp, Andricus quercuscalifornicus, but are exploited by a constellation of at least 20 other arthropods that feed on the galls, A. quercuscalifornicus, and each other.

These aren’t the only galls associated with the Valley Oaks. There are at least two more. One of which is fairly bizarre and the original inspiration for this post: the California Jumping Gall. This gall is also caused by a wasp, Neuroterus saltatorius. In contrast to the oak apple galls, these galls are tiny, only about a millimeter across. What they lack in size, however, they make up for in quantity. These galls form on the undersides of oak leaves by the hundreds of thousands. When they mature, they drop off the leaves, wasp larva still inside. Once on the ground, they start “jumping”. The larvae violently fling themselves around inside the gall, presumably to try to move it into a sheltered spot where they can finish out their life cycle and emerge the following spring to lay new eggs.

The galls are dropping now in my neighborhood, and the result is that sidewalks and gutters under valley oaks appear to be full of jumping grains of sand. It’s a pretty weird sight:

Here’s a link to another video:

ARKive video - California jumping gall wasp - overview

Well, that’s all I’ve got for now. I’ll end on another photo of an amazing Valley Oak.

Quercus lobata VALLEY OAK/ROBLE



Macrobrachium ohione, by Clinton and Charles Robertson, via Flickr.


