Rats, Bats, Oxygen’s Birthday, and Floating Metal

From CSIRO Science by email:

Flight of Bats

Some days, nothing would be nicer than to flap your arms and fly away, free as a bird. But could humans ever evolve wings? One mammal did, yet according to a new theory it wasn’t to take to the skies above, but rather to flutter to the ground below.

Wings are fairly complicated body parts. They require strong muscles to control them, an aerodynamic shape to achieve lift and bones that are both strong and light. One thing is for certain – wings didn’t just develop overnight. It takes many, many generations for such a feature to evolve.

It’s been suggested that an ancestor of modern bats grew membranes that allowed it to glide between the trees, probably to catch insects. The webbing of the more efficient hunters slowly evolved into wings. Many animals have developed similar body parts for gliding, including some lizards, marsupials, fish, and even snakes.

It’s an interesting theory, however, modern bats don’t glide. In fact, there are no species closely related to bats which glide. Not only that, ancient bats were cave dwelling insect eaters. They didn’t even have the ability to sense prey with echolocation like many of today’s bat species.

An alternative theory has been put forward to explain the transition from hands to wings. It suggests the bats used them to control their drop from the cave ceiling to the floor as they fluttered in from above. This controlled dropping behaviour is still seen in modern bats, especially in babies.

This news probably won’t help us humans sprout wings any time soon. But who wants the headache of falling onto cave floors, anyway?

Light Metal

Researchers at HRL Laboratories in the USA have created what they call ‘the world’s lightest material’ – and it’s made of something that should normally sink like a ball of lead.

The material is mainly composed of nickel, with small amounts of phosphorus included. Nickel is usually denser than steel, but this material is 100 times lighter than Styrofoam and is light enough to rest on the head of a dandelion.

How do you turn something so heavy into such a light material?

The key to answering this question is to look at the structure of the material. Think of a building such as the Sydney Harbour Bridge. It occupies a large volume and is also strong. However, the amount of steel used to make it is small compared to the space taken up by the tower – most of the space occupied by the bridge is filled with air. The researchers took a similar approach, just on a much smaller scale.

The new material is 99.99 per cent ‘open volume’ – in other words, it’s mostly empty. The remaining 0.1 per cent consists of hollow tubes of nickel and phosphorus that are 1000 times thinner than a human hair. The tubes are arranged in a lattice to make it strong while keeping it lightweight.

It is not only light, but has other useful properties too. It can absorb large amounts of energy, and is able to recover its shape after being compressed. Its inventors think it might have future uses in batteries, shock absorbers and assisting chemical reactions.

The development of materials such as this highlight that heavy metal may well be making way for something lighter.

Oxygen’s Birthday

Oxygen gas is a major component of Earth’s atmosphere and is essential for complex life on this planet. Earth is approximately 4.5 billion years old, but it hasn’t always had the oxygen-laden atmosphere that it has today.

Previous studies indicated the atmosphere’s oxygen gas developed around 2.7 billion years ago. New research linking geology, chemistry and biology suggests oxygen only started to appear in our atmosphere more than 200 million years later. How did scientists come to this conclusion?

Using ancient rocks from Western Australia’s Pilbara region, researchers searched for an element called chromium. The ancient Earth had many volcanoes which produced rocks containing chromium. The actions of some ancient microbes generated acid which dissolved the rocks and washed the chromium into the ocean.

Scientists can tell the difference between clues left by chromium from rocks and chromium in the ocean. There was little or no chromium in the oceans to begin with, so when the geological record started showing traces of oceanic chromium they inferred that these microbes had evolved.

What does this have to do with oxygen? The key is aerobic respiration. Aerobic respiration is a process where organisms use oxygen in air to kick start the chemical reactions needed to get energy. Without oxygen, aerobic respiration can’t occur. The microbes that produced acid which in turn dissolved the chromium were organisms respiring aerobically.

Chromium in the oceans instead of rocks indicates the existence of life respiring aerobically which indicates oxygen in the atmosphere. Similarly, the earlier lack of oceanic chromium indicates a lack of oxygen in the atmosphere.

The rocks that showed the transition between the types of chromium were 2.48 billion years old, which is where the scientists derived their new date for the development of oxygen in Earth’s atmosphere.

Rats are empathetic

Empathy refers to the sharing of another’s feelings. Humans and some primates are capable of empathy, but it isn’t clear which other animals might express this ability.

Research in the USA has shown that rats can display some empathic behaviour. This is the first time such behaviour has been observed in non-primates.

The researchers placed pairs of rats in an enclosure. One rat was trapped inside a see-through container, while the other rat was free to wander around. The free rat could let the other one out if it worked out how to open the door to the container.

Most of time, the free rats worked out how to open the door after a few days. Each time the experiment was repeated, the wandering rat set the trapped rat free fairly quickly.

This doesn’t necessarily demonstrate empathy. The free rat may have just been curious and formed a habit of opening the door, or it may have just wanted to play with the other rat.

The researchers tweaked the experiment so the container held either an interesting object, or was left empty. The rats only opened the cage when it contained another rat, demonstrating that it wasn’t curiosity or habit that motivated them to open it.

They then set up the experiment so that the rats would not have any other contact afterwards. The wandering rat still set the trapped rat free, showing that the rats didn’t just want to play together.

Even when the researchers put chocolate in one container and a rat in another, the trapped rat was freed first about half the time. When the container holding chocolate was opened first, the wandering rat still left some chocolate for its trapped mate to eat later.

These experiments suggest that empathy might not be restricted to primates. It also shows that, for rats at least, helping out a friend makes them feel just as good as eating chocolate.

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