The sequencing of the complete Neanderthals genome was one of the highlights of last year, not just because of the technical achievement involved, but because it confirmed something extraordinary about our own ancestry. It showed that everyone outside of Africa can trace around 1-4% of their genes to Neanderthals. Our ancestors must have bred with Neanderthals on their way out of Africa.
Then, later in the year, the same team revealed another ancient genome. This one belonged to a group of people called Denisovans, known only from a single finger bone and a tooth. They too had left genetic heirlooms in modern people. Around 5-7% of the genes of Melanesians (people from Papua New Guinea, Fiji and other Pacific islands) came from the Denisovans.
In this week’s issue of New Scientist, I’ve got a feature that explores our patchwork origins. I looked at what these ancient genomes mean for our understanding of human evolution. I also considered some intriguing questions like whether other Denisovan fossils have already been found, whether this human pattern is applicable to other animal species, how much you can tell from modern genomes alone, and whether we’ll ever get DNA from the ‘hobbits’ of Flores. Do check it out – it contains some great viewpoints from Svante Paabo and David Reich, two of the scientists who spearheaded the sequencing efforts, along with Chris Stringer, Milford Wolpoff, Alan Cooper and John Hawks.
The magazine’s on the stands for the next week, or you can read the piece online if you have a New Scientist subscription to read the full thing. If get round to it, I’ll try and stick up some of the transcripts from the interviews that I did for the piece. There’s some great stuff there.
Pollination is the process whereby plants turn animals into sex toys. With nutritious nectar, striking flowers (and the odd bit of deceit), they lure in animal carriers that can transport their pollen to another flower. These partnerships have painted the world in a resplendent palette of flowery hues. But pollination can create other feasts for the senses that are oblivious to us visually focused humans.
The Cuban rainforest vine Marcgravia evenia is pollinated by bats, which find their way around with sonar rather than sight. They make high-pitched clicks and time the returning echoes to “see” the world in rebounding sound. And M.evenia exploits that super-sense with a leaf that doubles as a sonar dish. It reflects the bats’ calls into strong, distinctive echoes, creating a sonic beacon that stands out among the general clatter of the forest.
The flying lemur must be one of the most inaccurately named animals in the world, for it cannot fly and it isn’t a lemur. This is why most biologists prefer to refer to it by its other name – the colugo. It lives in the forests of South-East Asia, where it glides (not flies) from tree to tree. From a standing start, it launches itself into the air with a powerful jump and spreads the massive membrane that runs from its chin to its hands, feet and tail.
The glide looks effortless, but Greg Byrnes from the University of California, Berkeley has found that it’s a surprisingly inefficient means of travel. Contrary to expectations, gliding actually takes up more energy than travelling the same distance by running and jumping through the canopy. So why do it? Byrnes has the answer – it saves time. For the busy modern colugo, gliding saves precious minutes that could be better spent on eating, mating or whatever it is that colugos do.
As we get older, our memories start to fail us. The symptoms of this decline are clear, from losing track of house keys to getting easily muddled and confused. Many of these problems stem from a failure of working memory – the ability to hold pieces of information in mind, block out distractions and stay focused on our goals. Now, a team of American scientists has discovered one of the reasons behind this decline, and a way of potentially reversing it.
Our working memory depends on an area known as the prefrontal cortex or PFC, right at the front of the brain. The PFC contains a network of nerve cells called pyramidal neurons that are all connected to one another and constantly keep each other buzzing and excited – like a neural version of Twitter. This mutual stimulation is the key to our working memory. As we age, the buzz of the pyramidal neurons gets weaker, and information falls more readily from our mental grasp.
But this decline isn’t the fault of the neurons themselves. By studying monkeys, Min Wang from the Yale University School of Medicine has found that the environment around the neurons also changes with age. And by restoring that environment to a more youthful state, he managed to ease some of the age-related decline in working memory.
The eleven specimens of Archaeopteryx are some of the most iconic and captivating fossils in existence. The fingers end in claws, the tail is long and bony, and the head – arched back in the throes of death – contains toothed jaws. But the splayed arms are lined with the faint but unmistakeable outlines of feathers. This was an animal halfway between a small flesh-eating dinosaur and a modern bird. In fact, Archaeopteryx is widely heralded as the first bird, occupying a pivotal position in the origins of this group.
But Xing Xu from Linyi University thinks that this first bird was nothing of the sort. The Chinese palaeontologist, who has found one fascinating dinosaur after another, has identified a new species called Xiaotingia that threatens to oust Archaeopteryx from its position.
By comparing Xiaotingia’s features with those of Archaeopteryx and other related birds and dinosaurs, Xu has drawn up a new family tree (see slideshow below). In it, Archaeopteryx sits with Xiaotingia among the deinonychosaurs, a celebrity-filled group of small, predatory dinosaurs that includes Deinonychus and Velociraptor. The lineage that led to modern birds perches on a different branch of the tree.
The rare South African iris (Lapeirousia oreogena) has a ring of six stunning purple petals, atop an equally vivid straw-like stem. The petals have white marks, which look like arrows pointing towards the centre of the flower. And that’s exactly what they are.
The iris is pollinated by the accurately named “long-proboscid fly”, whose tongue is twice as long as its body. It hovers over the flower and aims for the centre, driving its tongue deep into the stem to reach the pool of nectar at the bottom. As it drinks, its head pushes against the flower’s male organs, which deposit a dollop of pollen. When the fly leaves, it carries this payload to another iris. The flies and the flowers are intimate partners of evolution. The long tongues and stems have been perfectly aligned to give one partner a drink and the other a flying sexual aide.
All of this depends on the white arrows. When Dennis Hansen from the University of Kwazulu-Natal painted over the markings, the fly could no longer find the flower’s centre. The arrows are like a sign that says, “Insert tongue here”.
If you look carefully at the snout of a dolphin, you’ll see two rows of tiny pits, known as vibrissal crypts, When dolphins are born, these pits house whiskers that soon waste away to leave empty craters. It’s tempting to think that the crypts as useless evolutionary throwbacks to a time when the ancestors of dolphins used whiskers to feel their way about. But these structures are far from useless. In at least one species of dolphin, they can sense electricity.
Nicole Czech-Damal from the University of Hamburg discovered this amazing ability by studying the Guiana dolphin, also known as the costero. It looks a lot like the familiar bottlenose dolphin, but its vibrissal crypts are far larger. Back in 2000, these prominent pits intrigued Guido Denhardt, who decided to look at them using a heat-sensitive camera. He found that the dolphin’s crypts produce spots of intense heat, burning as brightly on the camera as the whiskers of harbour seals.
The heat spots implied that, contrary to what people had thought, the vibrissal crypts are fuelled by a strong supply of blood. They are not useless vestigial organs – these crypts do something.
Around a third of us are infected with a brain parasite called Toxoplasma gondii. This single-celled creature spreads to humans from cats, and has a tendency to change the behaviour of its hosts. Now, a team of scientists led by Frederic Thomas and Kevin Lafferty have found that countries where more people are infected with the parasite have higher rates of brain cancer.
This does not mean that T.gondii causes brain cancer, or even that the two are actually linked. Patricia McKinney, who studies brain cancer and was not involved in the study, says, “This is a technically sound hypothesis-generating paper and, viewed as such, is interesting. It doesn’t tell us much, other than pointing towards some further investigation.”
In Dunn County, North Dakota, the roads are paved with a unique danger. Over 300 miles of them are covered with gravel taken from the local North Killdeer Mountains. This rock is rich in a mineral called erionite that behaves not unlike asbestos. Both cause cancer, but according to animal studies, erionite is anywhere from 200 to 800 times more effective at it than its more famous counterpart.
Dunn County’s erionite gravel releases small brittle fibres into the air when lightly disturbed. They’re released by wheels driving overhead, the footfalls of pedestrians, or even the gentle scrapes of brooms and rakes. Once airborne, the fibres can find their way into the lungs of passers-by, accumulating in the surrounding cavity (the pleura). There, they cause chronic inflammation and, over time, a type of cancer called mesothelioma.
To date, no one in Dunn County has been diagnosed with mesothelioma as a result of erionite, but It is only a matter of time. The first such cases in North America have already been reported. And to see what the future holds, you only have to look 6,000 miles away at the Cappadocia region of Turkey.