Posts Tagged ‘selection’

Science that’s only skin deep

// December 3rd, 2010 // 2 Comments » // How Things Work, Recent Research, Science Communication, Sex and Reproduction

I’m a guest blogger for the RiAus, and this post also appeared on their fancy website. To tell the truth, I really wanted to call this post “Hormonally Yours” in homage to the Shakespeare Sisters (anyone?) but I’ll save it for another post.

Recently I was in Arnhem Land, visiting some Indigenous communities with a couple of friends. While I was there, I got pretty jealous of everybody’s darker skin. “It’s so well suited for Australia,” one of my friends lamented. “I should be in Norway or something.”

Pale skin like mine is not great for Australia. I tan pretty easily, but only after being burned bright red. While I was in the NT I slathered sunscreen religiously, but still managed to get a highly embarrassing burn on my lower back when I was building a sandcastle (an epic sand turtle, actually. Totally worth it.)

Anyway, enough about me and my weirdly tanned lower back (it’s been months! Why won’t it go away?) Let’s talk about Nina Jablonski, an anthropologist. In 2000 she suggested a new reason why skin colour varies so much. It’s not an adaptation to protect against skin cancer and sunburn, like I always thought it was.

It’s real job is to keep us highly fertile by maintaining a delicate balance between two key vitamins: Vitamin D and Folic acid.

Pica's skin tone matched her UVB exposure like her scarf matched her dress. Image by Monja Con Patines

Vitamin D is obtained through some foods, but mostly from drinking in sunshine. UV light turns cholesterol into Vitamin D, which then goes to either your liver or kidneys to be converted to an active form.

Once active it helps white blood cells like macrophages kill bacteria, and helps control levels of calcium and phosphate – important for building healthy bones.

Deficiency in Vitamin D causes rickets, a disease resulting in soft, easily broken bones and deformity which can lead to early death.

So getting enough UV (specifically UVB light) is important to not dying, and therefore having reproductive success later in life. It’s been backed up by Yuen, A. (Vitamin D: In the evolution of human skin colour DOI: 10.1016/j.mehy.2009.08.007)

Natural selection favours soaking up UV.

Penny stayed under foliage at noon to protect her folic acid. Image by Monja Con Patines

Folic acid is obtained in leafy vegetables and fortified cereals. Rather than being made by UV, the light can destroy folic acid by literally breaking it apart. (Jablonski, N. The evolution of human skin coloration DOI: 10.1006/jhev.2000.0403)

Critical for DNA synthesis, folic acid is essential during pregnancy when a lot of new cells are being made.

Folic acid prevents against 70% of neural tube defects in embryos. Its destruction by UV is bad news.

Natural selection favours avoiding UV.

So there’s an ideal amount of UV light that needs to get through the skin – enough to produce Vitamin D, but not too much to destroy all the folic acid. Getting the balance right for the environment you’re in means higher fertility, which drives natural selection

This is what Nina Jablonski thinks caused the evolution of skin colour through the sepia spectrum we see today. Dark skin, with high melanin, stops more UV light. That’s exactly what you want if you live in a place with a lot of sun, like places near the equator. Light skin lets more UV in, which is great if you live somewhere overcast and not very high on UV.

Understanding how your skin colour (NOT your race) influences these two vitamins is important in being healthy. It’s more important now than ever, because we humans travel a LOT.

Sadly, Australia is pretty high in UV and I am pretty white. Thank god for sunscreen.

Things are rarely that simple though, and I imagine there’s a few different things going on that connect UV light to skin colour.

On Tuesday the RiAus is holding an event called Skin Deep: Exploring human ancestry. They’ll be showing a preview of a new SBS documentary about skin colour scientific research, as well as results from the Genographic Project. Basically they took DNA samples from a lot of volunteers and some national identities, and now they’re giving us the goss on who’s related to who’s secret love child.

I’ll be there, I’d love to see you (though seats are limited.) I’ll be the one tweeting in the corner. Follow me @CaptainSkellett

Would love to hear from anyone who took part in the Genographic Project, and anyone who didn’t. Who would you most like to be related to? For me it’s David Attenborough, then I can dream of inheriting his voice.

Thought controlled computers? Recent research says yes.

// October 29th, 2010 // 6 Comments » // Recent Research

computer thinking

Image by Amarand Agasi

Imagine being able to control a computer with your mind!

No longer would we be tied down to keyboards, mice and touchscreens!

We need NEVER put down our coffee to work!

It’s not fantasy, that just happened.

Twelve subjects sat in front of a computer and looked at two superimposed images on a screen, focusing their mind on one of the pictures. The computer responded by making the image stronger while fading the other image away until only one was visible. They picked the image they wanted to look at, and made it so!

All the subjects had epilepsy, and had fine wires inside their brains to monitor seizures. These wires were attached to neurons and connected to the computer. Now not everyone has wires in their brain… YET. But to be honest I would consider it.

The images were picked during a screening process earlier that morning, which selected pairs that activated very different neurons. Marilyn Monroe and Michael Jackson were two famous faces used as pictures in the experiment. The Marilyn Monroe image might make some neurons fire faster, while the Michael Jackson image would make others fire. The pairs were used several times during the tests, half the time one picture was the target (ie. Marilyn) and the rest of the time, the other (Jackson.)

To quote the letter, published in Nature “The subject was instructed to enhance the target image from the hybrid image on the screen by ‘continuously thinking of the concept represented by that image.'” The concept? Like Marilyn Monroe and sex? Maybe. All the images were ones that would be familiar to the subjects, though I would like to know if you can choose between two completely new pictures.

Success rate (making the target picture take up the whole screen) was about 70%. Not bad… not great, but not bad.

This new research could shed light on how information is used in the brain, and how interactions between single brain cells let us make decisions. I personally hope this is the one of many steps towards real mind-control in the computer realm. Come on science, I’m sick of typing! Give me my mind mouse!

Here is the research paper. FYI, it was a bitch to read! Very confusing.

ResearchBlogging.orgCerf, M., Thiruvengadam, N., Mormann, F., Kraskov, A., Quiroga, R., Koch, C., & Fried, I. (2010). On-line, voluntary control of human temporal lobe neurons Nature, 467 (7319), 1104-1108 DOI: 10.1038/nature09510

Frilled dinosaur Mojoceratops is groovy baby, yeah

// July 11th, 2010 // 1 Comment » // Recent Research, Sex and Reproduction


Mojo: The libido. The life force. The essence. The right stuff. What the French call a certain… I don’t know what.

Mojoceratops was discovered when Nicholas Longrich from Yale University was looking at existing fossils from American Museum of Natural History in New York. They had been classified as another species, Chasmosaurus, but Nicholas believed they were something else. Dinosaur, thy name is Mojo.

Mojoceratops was about the size of a hippo and roamed the Alberta and Saskatchewan provinces of Canada around 75 million years ago. It nommed on plants only, like its relative the Triceratops. Anyone else having a flashback to the Land Before Time? Ducky was my favourite. That movie was epic. Anyway…

Most striking is the frill. All the Ceratopsids had frills, but Mojo’s was the largest and the most heart shaped. Nicholas thinks it was used for sexual courtship. The right side of the frill is larger than the left side, which indicates it was a display or weapon under intense selection. The same kind of asymmetry is also seen in deer antlers. Sexual selection fail though, the species only lasted for a million years. Did they lose their mojo?

Mojo means a talisman for attracting members of the opposite sex. Of course, Nicholas first came up with the name after having a few drinks. “It was just a joke, but then everyone stopped and looked at each other and said, ‘Wait — that actually sounds cool’ ” he said. Yes, yes it does. I think I have a new favourite dinosaur.

ResearchBlogging.orgLongrich, Nicholas R. (2010). Mojoceratops perifania, A New Chasmosaurine Ceratopsid from the Late Campanian of Western Canada. Journal of Paleontology, 84 (4), 681-694

Female fiddler crabs have sex with the neighbours

// April 20th, 2010 // Comments Off on Female fiddler crabs have sex with the neighbours // Recent Research, Sex and Reproduction

Fiddler Crab

Fiddler crabs may be little, but they have one big appendage, the CLAW! A weapon if ever there was one. Like a lance or an over-sized boxing glove, something about it just screams MAN. So it fits that male fiddlers are the gender so endowed.

Females have two little feeding claws. No giant claw. No weapon of any kind. Unless, of course, you count her good looks and killer form. Turns out that’s all she needs.

This research comes from the ANU (me own university), and there’s apparently a fiddler crab expert here that I have to meet. His name is Richard Milner, and the paper was published in Biology Letters.

ResearchBlogging.orgRichard N. C. Milner*, Michael D. Jennions and Patricia R. Y. Backwell (2009). Safe sex: male−female coalitions and pre-copulatory mate-guarding in a fiddler crab Biology Letters (6), 180-182 : 10.1098/rsbl.2009.0767

Fiddler crabs live in burrows, which are a place to hide when predators come along. Burrows are in high demand, and males will fight for squatting rights. Females can’t fight without a big-ass claw, instead they take over empty burrows.

Burrow-owning females would be sitting ducks for homeless males to come and kick them out, if it weren’t for the male next door.

Male fiddlers will defend the territory of nearby females. The study showed that if the intruder is a male, the neighbour will try to fight him off 95% of the time. That compares to just 15% of the time when the intruder was female. So male fiddlers like to be surrounded by female fiddlers. Go figure.

When picking a sexual partner, female fiddlers chose a neighbour who shares a territory border with her 85% of the time. The remaining 15% was made up of strangers, burrowless males and non-neighbour residents.

Part of that could be convenience, as females are at risk of predation while they search for a mate. Part of it could be gratitude. Part of it could be white knight syndrome, in which the big manly fiddler roughly dispenses of all piddly competition to claim the hand of the fair maiden. Damn I have a problem with personifying animals.

It boils down to one thing: Fiddlers exchange sex for protection. It makes me wonder whether some human relationships amount to much the same thing. Give me your thoughts and complete the following: Humans exchange sex for






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