Archive for Sex and Reproduction

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.

Platypus. Poisonous, egg laying mammal with ten sex chromosomes

// October 13th, 2010 // 7 Comments » // Recent Research, Science Communication, Sex and Reproduction, The Realm of Bizzare

Platypus

Image by Urville Djasim

Ah, the elusive platypus. The water dwelling animal with fur, webbed feet and a beak. It may just be the strangest animal on the planet. Not only does it look weird, it’s poisonous, can sense electricity, lays eggs and secrete milk through their skin, and have an excessive number of sex chromosomes.

It’s poisonous.
It is SERIOUSLY poisonous. The males have poison barbs under their front feet which they mainly use during the spring breeding season. One scratch from these babies and you will be in terrible agony.

My friend studied platypuses (yes, that’s the plural I checked) in honours and her colleague injected himself with platypus venom in the name of science. For months he had excruciating pain for months which did not respond to any painkillers, including morphine. Because of this quality, platypus venom could help scientists develop drugs which work differently to our current repertoire.

Research into platypus venom is lacking because it is hard to come across samples. But just last month researchers identified 83 possible venom genes using DNA extracted from an active venom gland. Some of the genes are similar to those in snakes, pufferfish and starfish. Now the platypus hardly evolved from a starfish. Instead, it’s an example of convergent evolution, traits that arise separately in different species and give a selective advantage. Illustrious journal Nature says platypus venom confirms the convergent evolution theory for venom. (Research paper Whittington CM, & et al (2010). Novel venom gene discovery in the platypus. Genome biology, 11 (9) PMID: 20920228)

Electroreceptor bill
Sharks use electroreception to find prey by sensing the electricity animals have in their body. Monotromes (mammals that lay eggs) including platypuses and echidnas, are the only mammals with the same ability, and the platypus is the strongest. Closing its eyes and nose when it dives, the platypus relies almost entirely on electrolocation and touch to find the tasty crustaceans it snacks on. Sharks and platypuses are hardly related, making this another yet another example of convergent evolution.

Electroreceptors are located in rows on the bill, which might help it find prey by noticing which receptors pick up the electricity first. We do the same thing with our ears, hearing noises at slightly different times tells us which direction the sound is coming from. When the platypus hunts, it moves its bill side to side, which might reveal how far away the prey is. It’s similar to how pigeons bob their head for depth perception.

Image by TwoWings

Laying eggs
A female platypus has two ovaries, but only the left one is functional. Why? We don’t know.

Eggs spend 28 days developing inside their mother’s body and 10 days outside. The babies (often called puggles) are born with teeth, which drop out as they mature.

The mother produces milk, but she doesn’t have teats or nipples. Instead puggles lick or nibble on her skin to drink, gaining nutrients and probably an immune system. Living in mud, platypuses are born with no immune system, making them worse off than human babies which have immature immune systems at birth and rely on colostrum to boost their protection.

Sex chromosomes
Since the platypus genome was sequenced in 2008, we know a bit about these strange sex chromosomes. We know that they are more similar to birds than mammals, suggesting that our own mammal-like reptile ancestors might have had sex chromosomes like the birds of today. But there’s one big difference that makes the platypus unique.

They have ten sex chromosomes. Males have five X and five Y. Females have ten X. Humans, in fact, almost all mammals have only two. During platypus sperm production, the sex chromosomes pair up as X1Y1, X2Y2, X3Y3, X4,Y4, X5,Y5, so they can split evenly to make sperm that have 5X or 5Y. Phew. After all that, I’m surprised the males have any energy left for mating.

Did the CIA spike a bakery in France with hallucinogens?

// August 27th, 2010 // 6 Comments » // Drugs, Poisons, Sex and Reproduction, The Realm of Bizzare, Unethics

On August 15, 1951 a small town in southern France called Pont-Saint-Esprit briefly entered the twilight zone. Hundreds of people reported acute psychotic episodes and physical symptoms such as nausea. They experienced traumatic hallucinations, and 50 of those affected were put in asylums. Five died. The event was later traced back to pain maudit – cursed bread.

In 2009 American journalist Hank Albarelli cited evidence that it was actually caused by CIA experiments into LSD. His book A Terrible Mistakesuggests the mass hallucinations experienced that day was a government funded field experiment into the newly found drug.

There would be potential for LSD to be used as chemical warfare – sprayed onto an army it would turn soldiers into… well… I don’t know but with guns involved I think it would be bad. I’m not sure if his conclusion is correct, but his article makes a compelling argument.

I have to say, conspiracy theories really do it for me. I think they’re great. Nothing like a little paranoia to keep you on your toes. There are, however, other opinions on what caused the Pont-Saint-Esprit madness.

One explanation is ergotism. Ergot is a group of fungi (most prominently Claviceps purpurea) which grow on rye, wheat and related grain-producing when-I-grow-up-I-want-to-be-bread plants. The fungus produces a neat little cocktail of alkaloid drugs which cause spasms, diarrhea, nausea and hallucinations – similar to those experienced at Pont-Saint-Esprit that fateful day.

In fact, the psychosis could have been caused by ergot or LSD, both have similar symptoms. LSD was first derived from the ergot alkaloid ergotamine. Controlled doses of ergot poisons have been used to treat migraine headaches and control bleeding after childbirth. Accidental, and dangerous, ingestion of ergot was known as Saint Anthony’s Fire (not to be confused with Saint Elmo’s Fire) for the monks of Saint Anthony who were really good at treating it. Ergotism was also blamed for Agent Scully’s hallucinations in the episode Never Again, where she gets a badass tattoo with some red ink that could have been coloured with ergot.

Greek myth time! In Ancient Greece annual initiation ceremonies were held for the cult of Persephone and Demeter. Demeter was the goddess of grain, farming and plenty, a bit of an Earth mother goddess with rich wheat coloured hair and a flowing dress. She guaranteed a good harvest. She had a daughter called Persephone, who loved the flowers. One day when Persephone was looking at some flowers in a field, Hades the god of the underworld noticed her, opened up the ground and abducted her. When Demeter noticed her daughter was gone, she was stricken with grief and refused to bring the harvest.

Persephone was trapped in the underworld for months on end. Desperate for her hand in marriage, Hades would offer her food, but Persephone know not to eat the food of the dead or she would never be able to leave. However one day Hades offered her a pomegranate, her favourite dish, and she ate six seeds.

Up in the mortal world, the land was dying. People were starving, having never experienced such famine. No matter how they prayed to the goddess she would not bring the harvest. Seeing the despair of the people, Zeus the king of the gods went down to his brother Hades and asked if he could bring Persephone back to her mother. Awkward conversation ensued.

Hades finally agreed, but oh noes! Persephone had eaten the food of the dead! The six pomegranate seeds meant that she had to spend six months of the year in the underworld as Hades wife. The other six months she would live with Demeter her mother. That’s why we have the seasons – autumn and winter when Demeter mourns, spring and summer when Demeter is reunited with her daughter.

Anyhoo, to be initiated into the Demeter and Persephone cult was called the Eleusinian Mysteries, some mysteries including this myth with added details. I think some of the mysteries included the use of pomegranate as a contraceptive (the link between fertility and death, perhaps.) You also had to fast during the initiation, and afterwards you would drink a barley drink called Kykeon and great revelations would be revealed.

Kykeon, made of barley, quite possibly tainted with ergot. Revelation or hallucination, you tell me.

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 babies respond to pregnancy stress, male babies don’t

// May 2nd, 2010 // 2 Comments » // Recent Research, Sex and Reproduction


Image by bettina n

Being stressed is not good for a pregnant mother, but how the baby reacts to the stress depends partly on its gender. Research led by Vicki Clifton from the University of Adelaide is finding out how stress changes the way babies develop.

When you’re pregnant, I imagine anything can stress you out. Were I up the duff (which I am not), I would most certainly stress about demon possessions… I can’t help but think of Omen and the Ring.

But it’s not just the mind. Asthma attacks, smoking and pre-eclampsia can put pregnant bodies under stress. The mother can communicate that stress to the baby while it’s still in the womb. Cortisol, a molecule involved in stress, causes changes in the placenta – but only if the baby is female.

A female baby will slow her growth when her mother is stressed. How thoughtful! By growing slowly she takes less energy and nutrients from her mother, which the mother might need to recover.

In contrast, a male baby does not change his growth with a stressed mother. He just keeps growing as fast as he can.

At first glance, it seems like a smart move for the male baby. Mother is stressed, something might be wrong, better grow as fast as you can and get the hell outta there. Unfortunately it’s not a good option. If there’s a second stressful event, the male baby is at risk of pre-term delivery or dying in the uterus. A female baby who has curbed her growth has a better chance of surviving.

The Darwin obsessed among you might wonder what evolutionary advantage is made by females reacting better to stress. If you have any ideas let me know, because I’m stumped.






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