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 😉

Wonders of Life; Brazil with Michael Palin

The third episode of Wonders of Life had the theory of natural selection as its theme, but once again didn’t approach it from the direction I expected. Instead Cox started by talking about how the most important element for life is carbon, because of its versatile chemical properties that allow it to form large & complex molecules with a variety of other elements. These molecules include proteins (which are the building blocks of organisms) and DNA (the instruction set). So he started by telling us about carbon being formed in stars, and then talked about how carbon in the atmosphere gets into organisms. The first stage is photosynthesis – where plants take CO2 and energy from the sun and turn them into sugar (a molecule with a carbon backbone) and O2. From here Cox moved on to talk about how the carbon that the plants are made up of move through the food chain – a lot of animals eat plants, but they are hard to digest because a lot of the carbon is bound up in molecules like cellulose & lignin which are important structural parts of plants. Termites solve this problem by farming fungus in their colonies, which digests the wood they bring it and then the termites eat the fungus. Giraffes in common with other ruminants have a complicated digestive system with multiple stomachs, one of which contains bacteria which help break down cellulose. Other animals take the shortcut of eating animals instead of plants – there was some great footage here of a leopard coming to pay a visit to the (very open!) car that Cox & camera crew were sitting in. I don’t think I’d want to go on safari, that’d freak me out!

Having established how animals get their basic components (to some extent) and talked about foodchains, Cox now moved back to DNA and how come there are so many different sorts of organisms. First he gave a brief description of how DNA codes for proteins (with not much detail) and then we talked about what drives mutations. He name checked the sorts of causes, and showed us one – cosmic rays. That was a pretty neat experiment, I don’t know that I’d seen a cloud chamber before and it was cool to see the cosmic rays passing through the vapour in the tank! He then talked about the incredibly high number of combinations of possible DNA molecules that there are if everything was down to random chance – most of which would be instructions for organisms that couldn’t live. So there must be something that constrains the set of combinations, and that something is natural selection.

I found his explanations here to be rather muddy to be honest, perhaps because I would’ve approached the subject differently if I was doing the explanation, perhaps because it was a high level overview of something biological told by a physicist so something got lost in the translation. But we got neat footage of lemurs in Madagascar, so that made up for it for me (and I hope that other people watching it who didn’t know what he was talking about in advance found it comprehensible). The gist of it was right, anyway – that variation between organisms affects their chances of survival (like having a slightly longer thinner finger for an aye-aye makes it easier for it to dig out insects from trees so that makes it easier for it to get food and to stay alive). If something survives more, it has more offspring so there are more like it in the population. And over time these changes can build up (the middle finger of an aye-aye looks really very different to that of other lemurs), and if the population is isolated in some way from the rest of its species then they will become a different species and no longer able to interbreed with the originals. Isolation can be geographical (he showed us how the break up of the supercontinent Gondwana had left Madagascar isolated for tens of millions of years), but it can also be within a geographical area by lifestyle or habitat. (After complaining about his muddy explanations, I think mine probably are too, ah well.)

The fourth episode was all about size, and how the laws of physics affect the size of organisms and the size of organisms affects which laws of physics are important to the organism’s everyday life. He started by swimming with great white sharks (he was in a cage so quite safe, but frankly I would really rather not have that experience personally), and using them to illustrate how the effort required to move through water constrains the shape an animal is – sharks, as with fish and aquatic mammals, are streamlined. He also talked about how living in water allows animals to grow larger, because the water counteracts some of the effects of gravity.

This moved nicely onto a discussion of how on land as animals get bigger they need bigger skeletons to support themselves, and this constrains the sorts of shapes they can be (big animals are proportionally bulkier) and the ways they can move. He illustrated this with Australian marsupials, and worked in an explanation of how kangaroos’ locomotion is so efficient because their elastic tendons store the kinetic energy that they have when they land, and then use that to spring back up again. But the main point of this sequence was to show us the relative femur (thigh bone) sizes of various marsupials both living & extinct. As the length of the bone increases (so the animal is bigger) then the cross-section increases significantly more (i.e. a five-fold increase in length but a forty-fold increase in cross-sectional area) – this is because the mass of the animal has increased in proportion with its volume, and volume increases as the cube of length.

Cox then turned from animals our sort of size (i.e. mice to elephants …) where gravity is the dominant force, and moved to the much smaller scale of insects. Particularly amusing in this bit was him dropping a grape then a watermelon off a balcony to demonstrate that small things bounce and bigger things … don’t. He talked about how this is due both to smaller things falling a bit more slowly (due to friction with the air) and also because big things have more kinetic energy that must be released when they hit the ground (because it’s proportional to mass, I think). And this is done via exploding in the case of the watermelon. So gravity isn’t the big thing for an insect, instead it’s the electromagnetic force, which controls the interactions between molecules – like the way you can pick up a small piece of paper by wetting your finger so the paper sticks to it. This principle is what lets insects walk up walls or across ceilings.

He then went on to talk about what the smallest possible size for an organism is. First for animals – of which the smallest known is a wasp that’s about 0.5mm long, and is a parasite that lays its eggs in the eggs of a moth that feeds on & lays eggs on macademia nuts. And then for bacteria (skipping viruses because they’re not really alive) – where the smallest possible size is 2nm (I think) which is constrained by the size of atoms. You can’t be smaller than the volume necessary to fit all your cellular machinery, and those molecules are the size they are because their atoms are the size they are.

And then Cox talked a bit about how size affects metabolism, and how that in turn affects longevity. Smaller things have a higher surface area to volume ratio (because as something gets longer its surface area goes up by the square of the length change but its volume goes up by the cube). And this means they lose more heat than a larger version. And if you’re an endotherm (like people are) and generate your heat inside you, then the more you lose the more energy you must use to replace it. So smaller animals tend to have a higher metabolism and generate more energy from more food more quickly. Bigger animals both don’t need so much energy (if they’re endotherms) but also there are other constraints that mean that they need to slow down their metabolism. I think one of those was that it takes longer for things like nutrients to get through the circulatory system and so cells at the periphery can’t run too fast otherwise they’d burn up all their resources before they could be replenished (I’m not sure I’ve remembered that right though). Then Cox finished up by using crabs to illustrate that things with a slower metabolism tend to live longer (and this segment made J shudder because he hates crabs!).

The second episode of Brazil with Michael Palin was called “Into Amazonia” and covered (roughly speaking) the north west of the country, including the capital (Brasilia) and some of the indigenous people. The programme was bookended by the two tribes he visited – starting with the Yanomami who are very isolated and trying to remain so and ending with the Wauja who are assimilating some bits of modern Western culture while still preserving their own culture. The leaders of both peoples are worried about the impact that government projects (such as dams and mines) will have on their way of life, and frustrated about the lack of consultation.

Palin also visited one of the last remaining rubber tappers – rubber was a major export from Brazil before the British got hold of some seeds and grew rubber trees in Malaysia. A bit of a sad segment, because the industry has just dried up & gone away. As a counterpoint I think this was where he got to swim with the pink river dolphins, which right up till they showed up I had assumed were going to be some sort of euphemism (particularly with the solemn young man explaining how sometimes girls turn up pregnant & they say the dolphins did it)!

I’m not going to run through everywhere he went or everything he saw, but the other bit that stuck in my mind was Fordlandia. This was a planned town, with a Ford factory, and it was supposed to be a perfect America (this is back in the 1920s). But what it was was a perfect failure, and all the remains today are some abandoned ruined buildings in the jungle.

Wonders of Life; Brazil with Michael Palin

Well, Brian Cox’s Wonders of Life series really didn’t start how I expected it to do. I suppose in retrospect it should’ve been obvious that a physicist would talk about the physics & chemistry of life rather than the biology! This first episode was asking the question “What is life?”. He made a brief detour to mention that this question is typically answered by reference to a soul or other supernatural cause, but then started to talk about the laws of physics and how life exists as a result of the ways these laws work (in the same way that a star exists because of how the laws of physics work).

Life probably got started in hydrothermic vents in the ocean – which are alkaline environments. The ocean of the time (3.5 or 4 billion years ago, or so) was slightly acidic, so there was a proton gradient set up between the alkaline waters of the vent & the acidic waters around about it. The protons moving along this gradient releases energy. This is the same mechanism by which batteries work – in this case the heat of the earth’s core drives the setting up of the gradient, and because of the first law of thermodynamics (conservation of energy) all of this energy must be released when the protons move down the gradient. The hydrothermic vents are also rich in organic molecules, and the energy drives the chemical reactions between these molecules. And the first life arises from that chemistry. All life uses proton gradients to get its energy – he showed us pictures of mitochondria from a variety of animals, but the same is also true of prokaryotes (which have no mitochondria).

At first glance life violates the second law of thermodynamics – that the universe tends towards disorder. Living things are obviously complex and over the last few billion years they’ve got more rather than less complex. I never quite follow this argument (physics really isn’t my thing) but I think what it boils down to is that whilst an organism is more complex it’s achieved that in a way that disorders its surroundings more than they would otherwise be. So yes living organisms are localised pockets of complexity but the universe as a whole is still more disordered than before.

He then moved on to talk about how come life isn’t still just chemical soup in rocks. And what keeps organisms the same as their parent organisms. The answer is DNA – the instruction set for making an organism. I was much amused by his DNA precipitation experiment – take cheek cells, add detergent, salt and alcohol, and hey presto! you have white strands of precipitated DNA in the alcohol layer in your test tube. That’s pretty much the basis of a lot of molecular biology labwork – only you don’t use fairy liquid or vodka. He then ran through the basic high level structure of DNA and talked about how it codes for proteins. And then proteins are both the building blocks & machinery of cells and organisms. The great thing about DNA as a molecule to store the instructions is how stable it is – he quoted 1 error per billion bases (I think) when duplicating DNA which is a pretty low error rate. And relatively small differences in the instruction set are enough to generate very different organisms – he pointed out we’re only 1% different from chimpanzees, 1.6% different from gorillas etc.

The second episode was all about senses. After a bit of scene setting he talked about paramecium, which are single celled organisms that swim about using wee hairs (cilia) in their cell membrane. When it bumps into something in the water the little hairs reverse direction and it moves away again. It does this using proton gradients – normally there’s a difference between inside & outside the cell, and when the paramecium touches something the membrane deforms & this opens channels in the membrane and the proton gradient equalises. The energy generated by this is used to switch the direction of the cilia and to open more channels (I think) which means the change in direction propagates right round the cell. This is the basis of how all our senses transmit the information back to the brain – this is how nerve cells work.

Cox then spent a bit of time talking about how different animals have different senses (and different dominant senses). Different species therefore sense the world differently to us – our dependence on sight & hearing, and our ranges of sight & hearing, aren’t some objective way of detecting the world. Like all other animals we have the senses that we need for our evolutionary niche. In this bit I was particularly amused by the footage from some experiments on frogs – if a small rectangle is move past a frog in a horizontal orientation it goes nuts trying reach it & eat it. If the same thing is moved past in a vertical orientation, the frog doesn’t even seem to see it. When it looks like a worm, then it’s detected, when it doesn’t look like lunch it’s not worth wasting energy paying attention to.

He then talked about human hearing while sat on a boat near some alligators. The point of the segment was that despite the little bones in our ears looking like they’re designed for the purpose, actually they’re re-purposed gill arches. And part way through this long process of re-purposing the bones are the reptiles, whose jaw bones are also re-purposed gill arches. So the alligators were illustration …I still wouldn’t’ve got that close to them myself!

And obviously he talked about sight. Rhodopsin, a pigment that reacts to light, has been around in organisms for a long time – way back to cyanobacteria which have existed for a couple of billion years. And Cox demonstrated how simple a basic eye actually is – even a “camera eye” like ours (retina which does basic light detection, some sort of case with a hole in in front, then a lens in the hole. Obviously the devil is in the details, but one thing Cox didn’t mention explicitly is that eyes are believed to have independently evolved several times (the figure I remember is at least 40 times, but I don’t know if that’s right). He then went diving to see an octopus in its natural environment – which is another animal with a camera eye like ours (and it evolved independently). Octopuses are pretty intelligent, and Cox speculates that perhaps intelligence is driven by the need to process the complex images that our sophisticated eyes produce. I’m not sure what I think of that, in the same programme Cox also showed us a mantis shrimp that sees more colours and detects distance more precisely than people – but there was no talk about them being particularly intelligent.

As I said, not quite what I expected from the name of this series, but that makes it more interesting I think 🙂

We also started watching a series about Brazil with Michael Palin. I tend to be a bit wary of travelogues like this – sometimes the bits where the presenter joins in can cross the line between funny & cringe-making for me. Palin normally stays about on the right side of the line, but only just. But it’s still interesting to see the places & people.

The first episode was about the north-east of the country & was titled “Out of Africa”. A lot of people in this region have African ancestry – a lot of the slaves brought from Africa to the Americas ended up in Brazil. Palin quoted a statistic of 40%, and said this was more than ended up in the USA, which I was startled by. This has noticeable influences on the art & culture of the region – one notable example is the religion of Candomble which mixes African and Christian elements.

Palin visited a few different places in the region & a variety of different sorts of groups & events. The ones that particularly stick in my mind were the cowboys who were participating a race to catch bulls. And the national park that consists of a region of sand dunes that are blown miles inland to an area with heavy enough rainfall that there are lakes in the middle of the dunes – which looks pretty surreal.