Tuesday, October 31, 2006

Sam, who is 11 asked us....

I have what might be a silly question. I've always wondered why humans have a large, pointy nose and great apes like chimps, orangutans and gorillas have hardly any nose at all? When did the nose evolve?

Well Sam, that is not a silly question at all, although it is a tricky one to answer. The first problem is looking at noses in the past. As you probably know, only the top of your nose has any bone in it, further down (where it is squishy) your nose is shaped by cartilidge, not bone, and as a result this is not usually preserved.

Currently the best supported idea is that a large nose helps you to keep warm. A large nose allows the air you breathe in to warm up a little and so it will not chill your lungs too much when you breathe in. Similarly, this change in tempreature combined with a large nose (and nasal cavity) helps you keep water in your body when you breathe out. You can see it when you breathe out on a cold day - there is always much more 'steam' when you breathe out through your mouth than your nose because you are losing more water vapour. But how does the evidence match up to this?

Well, first of all modern apes (chimps, gorillas, orangs and gibbons) all live in tropical climates, and as you correctly said, they tend to have small, flat noses. As early man / apes left the rainforests they would have encountered colder, dryer air on the plains and so the nose would have begun to evolve around then. This also explains when Neanderthal man (many of whom lived in high mountains) had a large nose, as do modern eskimos (innuits) who live in cold climates. So noses evolved to keep you warm and wet, but exactly when this happened is very difficult to say.

However, the nose also probably sticks out beasue we as humans have smaller jaws than other apes. As the muzzle moved back in early human, it left the nose sticking out in front of the face, rather than incorporated into it, as with things like gorillas.

Wednesday, October 25, 2006

Anonymous has sent us this query...

I have been told that there are creatures called pseudoscorpions, that look like real scorpions without the tail. Can you please tell me when and where the earliest forms of these creatures are from?

Pseudoscorpions do indeed look a bit like scorpions without the sting, but are probably most closely related to the quite large and very quick solifugids (also called sun spiders or wind spiders [pictured]). Pseudoscorpions are a group with a poor fossil record (they are very small and would easily be overlooked), and most of the ones we have are preserved in amber. However, the earliest fossil forms are known from the Middle Devonian (ca 390 million years) of Gilboa, New York State.

Anonymous sent us this...

Hi, I'm a 15 year old high school student. I have a question about birds and dinosaurs.

Dinosaurs evolved into birds right? A friend of mine doesn't think that could be true, because bird lungs are so different from any other animals. So my question is, how similar are dinosaur lungs with bird lungs?

There is now overwhelming evidence that dinosaurs did indeed evolve into birds. This includes dinosaurs having light bones, fused clavicles and a special bone in the wrist called the semi-lunate carpel which allows extended movements and ultimately flapping flight (not to mention feathered dinosaurs like the one pictured!). In fact you can trace so-called bird characteristics right back through the theropod dinosaurs. There are as yet no fossilised dinosaur lungs so we have to use other evidence to reconstruct what their lungs might have been like.

The strongest evidence is that air sacs which are found in the bones of dinosaurs are very similar to those in modern birds. Dinosaurs and birds also have uncinate processes on their ribs (little backwards pointing extensions) which we believe is further evidence for a bird like respiratory system in theropod dinosaurs as they make the ribs move in a similar manner in both.

Anonymous asked...

If you find and upward trend in the timberline over recent years, this means the climate is getting milder nowadays right? Does this mean global warming is really happening?

You are right, an upward trend is due to a milder climate. However, the about global warming is more difficult to answer. If we look at the big picture the climate on Earth has changed quite drastically - just think of Hannibal crossing the alps with elephants in Roman times. We have evidence that it was warmer then than it is today which goes along with higher reaching forests.

About 150 years ago it was very cold - almost a mini ice-age. Climate is therefore changing in intervals and whether we are still on an upward trend after the little ice-age or we have global warming (this expression nowadays indicates the human influence)is difficult to say. We are working hard to seperate the signals we get from the trees to be able to quantify the human and the natural warming.

Stuart wanted to know...

What is the recent evidence that says long-necked dinosaurs held their tails out straight? I liked the older idea that they dragged their tails on the ground.

Well Stuart, for a start there are many trackways known from sauropod dinosaurs and none of them show tail-drag marks (with perhaps one or two possible exceptions).

The longest-tailed sauropods, the diplodocids (Diplodocus, Apatosaurus, etc.) had a distinctive arrangement of the hips, in which the tops of the vertebrae (back bones) that make up the hips stick up very much higher than the main bits of the vertebrae. This arrangement would provide a strong anchor point for ligaments and muscles that would have kept the tail up off the ground.

The hips of shorter-tailed sauropods such as Brachiosaurus have less raised vertebae tops, so their tails may have been less horizontal than those of their longer-tailed cousins. Still, a brachiosaur's tail base would have been a good four meters off the ground, so the tail would have had to droop a long way bit to reach that far down!

Sara has asked us....

What was the largest trilobite?

The largest trilobite was Isotelus rex from the Late Ordovician (ca 450 million years ago) of Manitoba, Canada. A complete specimen is known and it is about 70 cm long and 40 cm wide. It was described by Rudkin et al. in the Journal of Paleontology in 2003.

Ian who is 10, asked us.....

Do you know if there are any shark fossils that are more than 365 million years old?

Fossil fragments of fish on the lineage leading to sharks date back 455 million years ago. In 2003, scientists reported discovering an articulated skeleton of a shark relative called Doliodus problematicus that lived almost 409 million years ago. Here's the abstract of the paper.

Ian also expressed an interest in moving animals, so here is a link to a page about locomotion (how animal move) at Leeds University in England. There are some nice videos here of some very early work done (in the 1870's!) on locomotion by the English scientist Edueard Muybridge. He used a special system of cameras to make a series of photographs of animals to see how they moved and then reassebled them into an early form of film.