Birth rates have decreased by about 2 percent in 2008, the first year since the beginning of the decade that rates did not increase, according to statistics from the National Center for Health Statistics. Many experts speculate that this drop is due to the recession. Still, birth rate statistics have not yet been finalized, and some believe that a decrease in immigration could account for the decrease in births.
As any parent knows, children are expensive, so in a shaky economy, it makes sense that fewer people would be having them. “It’s the recession,” said [sociologist] Andrew Hacker… “Children are the most expensive item in every family’s budget, especially given all the gear kids expect today. So it’s a good place to cut back when you’re uncertain about the future” [New York Times]. Perhaps not coincidentally, the two states with the largest decrease in births–California and Florida–are also the ones that faced the biggest problems due to the housing crisis.
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Circumcising men who are infected with HIV does not protect their female partners from the deadly virus, researchers have found. The Uganda-based study was stopped early due to “futility,” the researchers wrote in a study published in The Lancet, when it became clear that the women were not benefiting. The outcome was disappointing because circumcision has been shown to drastically reduce infection rates in men. But the researchers said that wide-scale circumcision is so effective in protecting men that [it] will still likely benefit women indirectly by reducing circulation of the virus in general [Reuters].
In 2007, the World Health Organization concluded that circumcising males reduced female-to-male transmission of the HIV virus by about 60 percent. The foreskin of the penis, which is removed during circumcision, is rich in cells that are particularly easy for the virus to infect. The theory is that removing this source of vulnerable cells makes infection more difficult [Reuters].
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To obtain a steady supply of unfertilized human eggs for medical research, New York’s Empire State Stem Cell Board recently authorized paying women to donate their eggs. The decision has set off a new round of discussion about whether paying for eggs is ethical. The board agreed that women can receive up to $10,000 for donating eggs, a painful and sometimes risky process…. Proponents say compensating women for their eggs is necessary for research, and point out that women who give their eggs for fertility purposes are already paid. Others worry that the practice will commodify the human body and lead to the exploitation of women in financial need [The New York Times].
At the annual meeting of the International Society for Stem Cell Research this week, British researcher Alison Murdoch described a less controversial “egg sharing” program that has met with success. Women struggling to conceive can obtain IVF at a discounted rate, in exchange for donating some of their eggs for research…. In 2008, Murdoch’s team had 191 enquiries from interested women and ended up obtaining 199 eggs from 32 couples. “We are getting donors and we are getting eggs,” says Murdoch. The team is using the eggs in experiments into “therapeutic cloning”, which could ultimately produce stem cells matched to individual patients [New Scientist].
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British researcher Karim Nayernia says he has produced human sperm from embryonic stem cells for the first time, but his claims have been met with some skepticism. Embryonic stem cells can develop into any kind of cell in the body, but researchers have struggled for years to produce reproductive cells from stem cells. The task is particularly difficult because it requires a complex form of cell division called meiosis, which reduces the number of chromosomes per cell by half [Nature News]. In the new study, published in the journal Stem Cells and Development, Nayernia says his team used a special cocktail of growth factors to transform stem cells into sperm.
But male fertility expert Allan Pacey says the lab’s creations are too abnormal to be called sperm. “I am unconvinced from the data presented in this paper that the cells produced by Professor Nayernia’s group from embryonic stem cells can be accurately called ’spermatazoa.” … Pacey said in a statement that the sperm created by Nayernia did not have the specific shape, movement and function of real sperm [AP].
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The union between the native California tiger salamander and the non-native barred tiger salamander, which was brought in huge numbers from Texas beginning 60 years ago by California bait dealers [The New York Times], has produced an alarming hybrid offspring. A new study of the hybrid’s behavior in artificial ponds serves as a reminder that invasive species can alter ecosystems in unexpected ways: in this case, by getting too cozy with the natives of central California.
The new hybrid “superpredator” grows larger than either of its parent species, and its bigger mouth enables it to suck up a wide variety of amphibian prey, said lead study author Maureen Ryan…. Mostly on the menu are smaller pond species, such as the Pacific chorus frog and the California newt—both of which were “dramatically reduced” in population by the hybrid in the experiments [National Geographic News].
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A reproductive strategy is essentially a cost-benefit analysis, as each organism has to determine how much energy to expend in its mating efforts. Most males, including humans, arrived at a strategy of producing vast amounts of tiny sperm, in hopes that among many matings, a few lucky sperm will manage to fertilize eggs. But some unusual organisms take a different approach and produce small amounts of “giant sperm,” and a new study reveals that some organisms had adopted the strategy as early as 100 million years ago.
The giant sperm strategy is found in a handful of modern organisms, including the fruit fly, which is only a few millimeters in size but can produce 6 cm-long (2.5 inch) coiled sperm…. Now the discovery that ostracodes, an extinct ancient class of arthropods, displayed the same trait shows that making giant sperm is a long-standing and evolutionarily successful reproduction strategy [Reuters]. Using a sophisticated imaging technique to study the fossilized soft organs in a tiny ostracode, a bivalve creature only one millimeter long, researchers proved that expending a great deal of energy to produce giant sperm has paid off for some species. “Now we can show that in spite of the costs, it must be a successful way to reproduce, since it ’survived’ for such a long time” [LiveScience], says lead researcher Renate Matzke-Karasz.
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The seeds that twirl down from maple trees every spring can fly as far as a mile, with each wing-shaped seed spinning like a whirligig on the air. Studies have shown that the seed’s whirling, called auto-rotation, gives it extra lift, but why this occurs has never been explained. It took an aerospace engineer, David Lentink of the Wagenigen University in the Netherlands, to figure it out [The New York Times].
Lentink and his colleagues first studied how a model of a maple seed moved in a tank of oil, and then filmed a real seed falling through a smoke-filled wind tunnel, which allowed them to observe the air currents around the seed. The images the team obtained showed that a swirling maple seed generates a tornado-like vortex that sits atop the front leading edge as the “helicopter” spins slowly to the ground. This leading edge vortex lowers the air pressure over the upper surface of the maple seed, effectively sucking the wing upward to oppose gravity [Live Science].
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A hummingbird in love can perform aerial stunts that put fighter pilots to shame. In a new study, researcher Christopher Clark captured the male hummingbird’s daring dives with cameras that can capture 500 frames per second. To get the footage, Clark set out a caged female, or even a stuffed female on a stick, to inspire birds to dive right in front of his video cameras [Science News].
In the study, published in the journal Proceedings of the Royal Society B, Clark observed the Anna’s hummingbird, a tiny bird native to the American southwest. In the male’s courtship display he dives down dramatically with his wings pressed to his sides, and then dramatically stretches out his wings and tail feathers to break his momentum and bring him swooping back up into the sky. Clark says that the maneuver sets some records. When measured relative to the length of their bodies, the birds’ top speed, he said, was “greater than [that] of a fighter jet with its afterburners on, or the space shuttle during atmospheric re-entry” [BBC News].
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In some lizard species, it’s not just genetics that determines whether males or females will clamber out of hatching eggs. Some species are also governed by nest temperature, like the the three-lined skink lizard: Seven years ago, Australian biologist Rick Shine showed that low nest temperatures could overrule genetics, and cause embryos to develop into males. Now, Shine and his colleagues have taken their skink research a step farther, showing that the size of an egg’s yolk also plays a mysterious role in the ultimate sex of the offspring.
Physiologist Rachel Bowden, who was not involved in this research, says the study “muddies the water” for everything researchers thought they knew about sex determination in lizards…. “It’s clear that they have sex chromosomes. But it’s also clear that those sex chromosomes can readily be overridden by some other factors. So, the process that leads to sex determination might be fairly plastic” [The Scientist].
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When a heterosexual Humboldt penguin couple rejected their unhatched egg this spring, zookeepers at Germany’s Bremerhaven Zoo found a happy home for the abandoned egg in the nest of gay penguin pair, Z and Vielpunkt. “Another couple threw the egg out of their batch,” the zoo’s vet said in a statement. “We picked it up and put it in the nest of the gay penguins” [The Advocate]. The couple then incubated the egg for more than a month before hatching a healthy chick that is now about four weeks old.
Z and Vielpunkt have been caring for the chick just as a heterosexual penguin couple would, say animal experts. They’ve been taking care of their chick around the clock; it’s still too young to feed itself, so the dads feed him fish mash [Los Angeles Times]. But the pair is not the first same-sex penguin couple to raise a child: a pair at Central Park Zoo in New York also hatched an egg, but only after they tried to incubate a rock until they were given an abandoned egg. Another male penguin couple were removed from their colony in a Chinese zoo last year when they repeatedly tried to steal eggs from male-and-female pairs. (In a rather ingenious move, they actually replaced the eggs they were stealing with rocks.) [Los Angeles Times]
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A tiny ivory carving of a busty woman may be not only the oldest known example of erotic art–it may be the oldest art depicting any human figure at all. Named the Venus of Hohle Fels after the cave in southwestern Germany where it was recently excavated, the object dates to at least 35,000 to 40,000 years ago, based on more than 30 radiocarbon measurements conducted at the site [Discovery News]. The statue is also “bordering on the pornographic” by our modern standards, one expert says, with its huge, bulbous breasts and oversized genitalia.
Germany’s southern caves were presumably inviting sanctuaries, scholars say, for populations of modern humans migrating then into central and western Europe. These were the people who eventually displaced the resident Neanderthals, around 30,000 years ago. Dr. Conard reported that the discovery was made beneath three feet of red-brown sediment in the floor of the Hohle Fels cave. Six fragments of the carved ivory, including all but the left arm and shoulder, were recovered. When he brushed dirt off the torso, he said, “the importance of the discovery became apparent” [The New York Times].
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Males of the spider species Harpactea sadistica have a violent way of increasing their odds of reproductive success. In the midst of a mating tussle, the male stabs his spiked copulatory organ (pictured) into the abdomen of the female, in order to deposit his sperm directly into the female’s ovaries.
This process, known as traumatic insemination, is common among many hermaphrodite species as well as some insects with separate sexes, most famously the bed bug. But it has never before been observed in other arthropods. “Now we have a very odd biological phenomenon in an unrelated taxonomic group…. It’s like finding a peacock’s tail in a non-bird species” [The Scientist], says Mike Siva-Jothy, who has observed the behavior in bed bugs.
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A group of researchers has found stem cells in the ovaries of mice that they say can be prodded to become new eggs, which can then be fertilized to produce healthy offspring. The provocative findings challenge one of the most fundamental assumptions in biology: that female mammals, including women, are born with all the eggs they will ever have…. While much more research is needed to confirm and explore the findings, the work raises the tantalizing possibility that it could someday lead to new ways to fight a woman’s biological clock, perhaps by stockpiling her egg-producing cells or by stimulating them to make eggs again [Washington Post].
In the study, published in the journal Nature Cell Biology, researchers wrote that the stem cells were cultured for more than six months and then transplanted into the ovaries of infertile female mice, … adding that eighty percent of these mice went on to produce offspring after natural mating [Reuters].
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The preference for sons in traditional Chinese families has led to a vast gender disparity in China: A study has found that there are currently 32 million more boys than girls under the age of 20. While Chinese officials have acknowledged that the country’s “one-child” policy has led to a gender imbalance, the new study offers the first hard data on the extent of the disparity. The study included nearly five million people under the age of 20 and covered every county in China. It found that overall ratios of boys were high everywhere, but were most striking among the younger age group of 1-4 years, and in rural areas, where it peaked at 126 boys for every 100 girls [The Wall Street Journal blog].
With the greatest imbalance occurring with very young children, the researchers say that China will be grappling with the problem for 20 years. The imbalance is expected to steadily worsen among people of childbearing age over the next two decades and could trigger a slew of social problems…. “If you’ve got highly sexed young men, there is a concern that they will all get together and, with high levels of testosterone, there may be a real risk, that they will go out and commit crimes” [AP], says study coauthor Therese Hesketh.
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Human females may get offended at dates who expect a little something extra after they buy a steak dinner, but for chimpanzees, the exchange may be a fair one [Reuters]. A new study of a chimp community living in the western African nation Côte d’Ivoire has found that males regularly share meat from their hunting expeditions with females, and get sex in return.
The researchers observed males sharing meat with females in estrus, who have sexual swellings that indicate their current fertility. More surprising was that males shared meat with females that didn’t have sexual swellings, perhaps in hopes of future success, the researchers say. The sex “may not necessarily occur immediately—it could occur sometime in the future,” said study co-author Cristina M. Gomes [National Geographic News]. The findings, she says, support the theory that chimps can engage in long-term planning, anticipating future events and remembering past interactions.
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