Humans have worm-based brains

For some of us, feeling like we have the brain of a worm is a common experience.  But new research has shown that our brains may actually have evolved from worms, making the origins of the nervous system much older than previously thought.
Vertebrates like us, insects and worms evolved from the same ancestor, but their central nervous systems are different and were thought to have developed only after the split. But new research from the European Molecular Biology Laboratory (EMBL) in Heidelberg now suggests that the last common ancestor of vertebrates, insects and worms already had a centralised nervous system similar to that found in vertebrates today.
The last common ancestor we shared with worms an insects was a simple creature called Urbilateria.  Since then, vertebrates have developed a nervous system with a brain and a spinal cord running down the back, while worms and insects have a rope-laddder-like chain of nerve cell clusters running down the belly.  And other insects have even stranger nervous systems, made of nerve clusters all over the body.   So how did all these systems spring from one ancestor, Urbilteria? And what did Urbilateria’s nervous system look like?
To answer this, the researchers, led by Detley Arendt, studied a simple sea worm, called Platynereis dumerilii.  Platynereis can be thought of as a kind of “living fossil”, which still lives in the same environment as the last common ancestors like Urbilateria. The worm also has a prototype invertebrate nervous system, thought to similar to that in our common ancestor.
Arendt and his group investigated how the developing nervous system in Platynereis embryos gets subdivided into the regions that later on give rise to the different nervous structures. The researchers studied the genes involved in the process, and compared them with the genes that control the development of the vertebrate nervous system. They found some surprising similarities, showing that the molecular landscape in the developing nervous system is virtually the same in vertebrates as in the Platynereis worms.
The researchers argue that such a complex arrangement could not have been invented twice throughout evolution, so it must be the same system at work, hat has been inherited from our primitive shared ancestor.  The next challenge is to figure out why worms have their nervous system in their bellies, while vertebrates have theirs in the back.

21st Apr 2007

Heat Triggers Sex Change in Lizards by Turning Off Genes

A new study out this week has shown for the first time that heat causes lizard eggs to change sex by switching off a key gene.

While that may not sound especially revolutionary, it actually means that biologists will now have to think completely differently about the way sex is determined in animals.

Previously it was thought that sex is determined in one of two ways.  For humans, and other mammals as well as birds and some amphibians, an individual animal is male or female depending on the sex chromosomes it inherited from its parents.  Human females have two X chromosomes, while males have one X and one Y.

For other animals, sex is controlled without the help of sex chromosomes – but instead is governed by temperature.  so, in some reptiles, like crocs and turtles, the number of male and female young hatching from a clutch of eggs depends on the temperature that the eggs were kept at while they were being incubated.

Now researchers from the Institute for Applied Ecology at the University of Canberra in Australia have discovered that one of their native lizards, the central bearded dragon lizard, not only have sex chromosomes but they are also affected by temperature – if eggs are incubated at higher temperatures then ones that would develop into males based on their chromosomes, instead turn into females.

The researchers think that temperature is effectively switching off the affect of the male gene – the presence of which makes an individual a male, a bit like the Y chromosome in humans. By switching off that gene, the unborn lizard becomes female.

As well as rocking our understanding of how sex is determined, this latest piece of research might also have important implications for the survival of species in the face of climate change.  If there are too many females being produced and not enough males for them to partner with, it can spell serious problems for the survival of species, since an increasingly warm world could be an increasingly female world, at least as far as lizards go…

21st Apr 2007

Looking at Lemmings

It’s a common belief that lemmings commit suicide by flinging themselves off cliffs en masse.  However, this isn’t actually true. Like most of us, lemmings are quite keen to stay alive, but their existence may threatened by climate change.  The little rodents live up in the Arctic, and so the Wildlife Conservation Society thinks that they may be susceptible to the impact of changing climate.
A change in the lemming population could have big knock-on effects in the wider ecosystem, as they are an important food source for a number of predators, including arctic foxes, birds of prey, weasels, wolverines, and grizzly bears. In fact, the population of many predators fluctuates in response to dips in lemming numbers.
The most important thing for lemmings is snow.  They live in deep snow burrows, so the snow has to be thick enough to insulate them from the cold.  If snow arrives late, or melts early, then this could actually mean more chilly spells for the lemmings. Also, unusual warm weather in the Arctic winter means freezing rain, and cycles of thawing an freezing.  This can coat plants with ice, meaning the lemmings can’t eat their usual food.
Next month, the Wildlife Conservation Society plan to launch a major study to look at how the lemming population, and their predators, are changing. It’s one part of a large Canadian project,  called the Arctic Wildlife Observatories Linking Vulnerable Ecosystems, which gives you the rather clever acronym ArcticWOLVES.

21st Apr 2007

King of the Swingers

As a famous character in a great Disney cartoon once sang about, it turns out that Orang utans really are king of the swingers because they know just the right way to swing their way through the forest without wasting too much energy.

That’s according to a new study published this week by a team of scientists from Birmingham University, here in the UK.

To get around the forest and move across the gaps between trees, orang utans can’t simply climb along to the end of a branch and grab onto another branch of the next tree because they are too big and the thin branch ends wouldn’t hold their weight.

Also, dropping down to the ground, walking along to the next tree and then climbing up another tree or a vine is also not a great option either, because it exposes the orang utans to predators on the ground like tigers.

Instead, what scientists watching orang utans in the wild have discovered is that the great orange apes bridge the gaps between trees by choosing young trees with springy bendy trunks which they rock backwards and forwards in any direction they want - a technique known as tree sway. If they swing far enough they can then grab onto the branch of the next tree and relatively effortlessly continue their journey.

The researchers estimated that the orangutans use about half the energy using their tree sway method compared to jumping directly between trees and only one tenth the energy they would have to use if they climbed down to the ground each time they wanted to move across a gap.

21st Apr 2007

Science Update: Deserts

Bob -   This week for the Naked Scientists, we’re going to talk about two deserts on opposite sides of the world. I’m going to tell you why scientists think the already dry American Southwest is drying out even more, but first, Chelsea has this report on a desert region in Africa that’s been very much in the news.

Chelsea -   The war-torn Darfur region in Sudan was once home to an ancient mega-lake, and some of that water may still be there. Geologist Farouk El-Baz is director of the Boston University Center for Remote Sensing. He says satellite radar data show that thousands of years ago, Darfur was a savannah with a lake the size of the state of Massachusetts. His team is certain that deep wells could tap the remains of that lake.

Farouk El-Baz (Boston University):  And the reason that we are absolutely convinced that this is the case is the fact that we do have a very similar structure just north of the area we’re talking about, in the western desert of Egypt, and it has plenty of water. There are now 500 wells drilled through it, and there is potentially something like 150,000 acres of arable land, and the water that’s available there could supply all of these acres for agriculture over 100 years.

Chelsea -   Since the brutal conflict in Darfur is in part over water, there’s hope that this new source could help bring peace.

Bob -   Thanks, Chelsea. By mid-century, the American southwest and parts of northern Mexico may settle into a permanent drought: one that, for dryness, could rival the Dust Bowl in the Depression-era Great Plains, or the Southwest's own severe drought of the 1950's, the worst of the century.  This is from climatologist Richard Seager of Columbia University's Lamont Doherty Earth Observatory. He and his colleagues analyzed 19 different climate models used in the Intergovernmental Panel on Climate Change's Fourth Assessment Report. The data suggest that a drying trend has already begun in sub-tropical areas worldwide.

Richard Seager (Lamont Doherty Earth Observatory):  It begins right at the junction of the 20th century and the 21st century.  So the models say that yes, this should already be underway.

Bob -   Seager says that unlike past droughts, the current drying trend is caused by changes in air circulation due to global warming. A long-term drought would increase the strain on already-overtaxed water sources like the Colorado River.  That could force the region's rapidly growing population to re-evaluate its priorities.

Richard Seager:  Throughout the Southwest, it's not people that are the main users of the water, but it's actually agriculture, even in desert states like Arizona... so, there's going to be some sort of difficult decisions that are going to have to be made about how the diminishing water resources get allocated.

Bob -   He also notes that although there's probably nothing we can do to stop the drying trend completely, restricting greenhouse gas emissions may potentially limit just how bad it gets.

Chelsea -   Thanks, Bob. We’ll be back next time with stories about the things that profoundly influence your buying decisions like, of course, celebrities. Until then, I’m Chelsea Wald

Bob -   And I’m Bob Hirshon, for AAAS, The Science Society. Back to you, Naked Scientists!

April 2007

Fire Piston

You may have noticed that if you pump up a bicycle tyre your pump gets hot, we find out why, and do a slightly more extreme version

What you need

We used a large "fire piston" this is an ancient fire lighting device from SE Asia. The one we used is basically a large transparent bicycle pump, but with nowhere for the air to get out at the bottom.

Some cotton wool is teased out and then placed in the bottom of the cylinder. The plunger is then pushed down incredibly hard.

What may Happen

When the plunger is pushed down very fast the cotton wool gets immensely hot and bursts into flames. This was used in the Burma, Malaysia Borneo region as a way of starting fires. These were made of horn or bamboo and would light a small piece of tinder. It is thought that Rudolf Diesel saw one of these and it gave him an idea..