Ice Age Giants; Wonders of Life

Ice Age Giants is a new series presented by Alice Roberts about the large animals that lived during the last ice age. It’s a nice blend of Roberts talking to various experts & looking at fossils, and cgi of what they think the landscape & animals look like. Of course I always wonder what we’re wrong about looking at stuff like that, but it’s cool to see.

The first episode was all about animals in North America. She started with Smilodon fatalis, the sabre-tooth cat – this segment mostly concentrated on how it killed its prey. The sabre teeth are actually pretty fragile (relatively speaking) and one might think that they would be easily broken by getting stuck in struggling prey. They also can’t kill the way modern big cats do – like lions – because they actually suffocate their prey by crushing the windpipe between their jaws or pinching the nose shut. But if you look at the width that a sabre-tooth cat’s mouth can open (to an angle of 120°, twice as wide as lion’s) and the big boned & heavily muscled front legs then another hypothesis becomes apparent. The cats killed by pinning down their prey (to keep them still) then slicing through the throat & ripping out the windpipe or cutting the various arteries there.

Roberts then moved on to talking about the Shasta ground sloth – a large (grizzly bear sized) relative of modern sloths. She visited a cave that had been a ground sloth lair with a palaeontologist who studies these animals – the cave contained a very large amount of sloth excrement. Apparently it hadn’t rotted because the conditions in the Grand Canyon (where this was) are so dry. They looked at bits of this & could see that sloths clearly didn’t digest their food all that well (bits of twig & so on still recognisable). And there was even a large pile near the back of the cave that had distinct layers and so on running from ~40,000 years ago through to ~20,000 years ago – a bit like the geological record in rocks.

Next up were glyptodonts, an animal I’d never heard of before. In the cgi sequences they looked a bit like massive armadillos or turtles on steroids. According to the palaeontologist Roberts talked to these creatures are often found belly up – if they die in water then the weight of their shells makes their body flip over & they sink to the bottom upside own. They had a reconstruction of two of these fighting – they don’t just have massive armoured shells and armoured tails, they also have little armoured hats that look about right for protecting the brain as two of them clash together in a dominance fight (a bit like stags).

Roberts then went to look at large standing rocks with a scientist who is looking at the weathering/wear patterns on the rock. He thinks that the smooth patches must’ve been polished by animals rubbing up against the rocks to scratch their backs as the wear patterns don’t look like any of the other possible causes he’s investigated. The lower bits & bobs could’ve been many things (including modern domestic livestock), but the 14 foot high patches were almost certainly mammoths! The Columbian Mammoth was bigger than the Wooly Mammoth of Europe, and was even taller than modern elephants. And they weren’t hairy, I had no idea you got bald mammoths.

And the last segment of the programme was about the La Brea Tar Pits. Which as soon as she said the name I remembered I knew of them, but I’d forgotten till I was reminded. These are in California, and are a source of natural asphalt. It’s sticky (obviously) and sometimes creatures get trapped in it and die – and to date 3,000,000 specimens of 600 different species of fossils from the era of the ice age have been found in these pits. I don’t think they’ve actually dug through much of them – there was one batch found when an oil company was digging up the tar, and another batch was dug up when some where wanted to build a car park. They’re still processing this batch – it was moved in blocks so they can now excavate it properly. So they aren’t just finding the big animals (which include sabre-tooth cat kittens!) but also the little ones like snails & beetles and such. And this is generating a lot of useful information about the general environment and climate in the area during the ice age period.

Once upon a time I wanted to be a palaeontologist, but I’m not really an outdoorsy enough person to do the work. But you can picture me watching this programme filled with glee and bouncing up & down a bit going “oooh, look at that, isn’t that cool?”. And there’s another episode next week! 🙂

We’ve now finished watching Brian Cox’s Wonders of Life, the final episode was mostly looking at the physical & chemical properties that make life possible on our planet. The ingredients that make it home, as he put it.

So he started out with water, and explained hydrogen bonds. These form because water molecules are polar – the electrons in the molecule are more around the oxygen atom than the two hydrogen atoms. So the oxygen atom has a slight negative charge & the hydrogen ones are slightly positive. These means that bonds called hydrogen bonds form between the oxygen of one molecule and the hydrogens of another. Which makes a body of water not just a bunch of separate molecules but instead it’s a more cohesive thing. This makes water a good solvent (I’m not sure I followed this, but I’ll take his word for it), and so it carries many of the other nutrients we and other life forms need. Its solvent properties also make it a good place for our own internal chemistry to happen – and all living things have a large percentage of water. The cohesiveness of water also gives it surface tension. Cox demonstrated this by looking at pond skaters, which live on the top of water supported by surface tension. Surface tension is also how water moves through plants, all the way from the roots to the leaves.

Next up was light, and he started by looking at all the ways that the light from the sun is harmful concentrating mostly on talking about UV. UV light damages DNA and can burn skin, so most animals and plants have some sort of adaptation to prevent this. Humans (and other animals) use melanin, which is a brown pigment that is particularly good at dissipating the energy of the UV radiation. Cynaobacteria evolved a different way of dealing with light – they absorbed & used the energy. The coupling up of two energy using systems to take the energy of light plus CO2 and turn it into sugars (ie food) and O2 appears to’ve evolved only once – plants do it too using organelles which are descendants of cyanobacteria that now live inside plant cells. And this provides the third of the ingredients we need for our sort of life – oxygen. He went into a cave with a sulphurous lake to look at the sorts of organisms that life in oxygen-free environments – slimy ones, it seemed.

And the last of his ingredients was time. Both the sort of time that gives us our circadian rhythms and gives the monarch butterflies their navigational systems, and also the sort of time that gave us a chance to evolve. If you look at the history of life on this planet there’s a loooong couple of billion years before you get beyond single celled organisms. Even a billion years to get from simple cells (prokaryotes) to complex cells (eukaryotes). Cox was asking “is it necessary to have all that time?”, and saying that we don’t know because we only have one sample so not enough data. I’m not sure I agree – there’s clearly random chance involved in whether or not the right mutations came up, so it could’ve happened immediately or it could never’ve happened. So I don’t think the length of time it did take is significant or necessary. It’s just indicative of how rare a chance it is – because each of the big jumps (non-life -> life, simple -> complex cells, single celled -> multicellular, development of photosynthesis etc etc) has only happened once despite the four billion years available (a third of the age of the universe, don’t forget).

Overall I’ve enjoyed watching this series. It really wasn’t what I was expecting (though I’d find it hard to tell you what I was expecting) but in retrospect it’s obvious that a physcist would tell us about the physics & chemistry behind the biology. And it was more interesting for me because it wasn’t what I was expecting. I did feel he was stronger on the physics & chemistry than the biology which sometimes felt a bit like he was saying things he didn’t quite understand. A bit like me talking about physics to be honest 😉