Did fire make our ancestors lose their fur?
Did our ancestors lose their fur about the same time they mastered fire?
Chris Smith put this question from Colin on the Naked Scientists forum to human origins expert, Lee Berger. Dinosaur expert Jason Head, from the University of Cambridge, then explained how dinosaur skin wasn't quite as crocodile-like as is often depicted...
Lee - I think the first part is what’s the difference between fur and hair? We often speak of humans as having hair and animals as having fur, and the answer is nothing, it’s the same thing. It’s a semantic argument. But the early part of our understanding of where we see a sort of "fining" and separation of hair in humans is probably at the root of that question, and we kind of tie it to two things. One is thermoregulation - the idea that we need sweat glands. We sweat on our skin to actually lose heat. We believe that happened with long distance walking and running, and this longer limb period is generally associated with the origin of the genus Homo. So the answer is maybe it was associated with the fire because those two things go back a very long way. Fire, the oldest fire that we’ve got is about 1.3 to 1.5 million years. It’s surprisingly hard to see in the fossil record, but that morphology, that wider chested, long-legged anatomy that signals sweat glands maybe 2 million years ago, but we don’t trust these dates these days. We keep finding something every other week that pushes something further back or in a different line!
Chris - We take for granted our access to fire in the modern era, but what would it have taken for ancient ancestors of humans to have mastered the art of fire making, and nurturing, and using fire to good effect?
Lee - Well, having spent the last several years down a deep dark hole looking at homo naledi fossils I’ve pondered fire a lot, and the idea of fire as both a heating source but also as a light source to move into these more remote, underground chambers. Fire is a tricky thing - most animals hate it. They hate it instinctively if you’re a terrestrial animals for very obvious reasons, fire is a very scary thing.
At some point in our past, and that is somewhere in our very distant past. A million and half, two million maybe, I would suspect even further than that, part of our family tree began catching fire, and catching fire is probably a first key to that. Manufacturing fire, we don’t really have any evidence of until the last several hundred thousand of years. And generally the early parts of that are controversial in of themselves because there’s a big difference between catching fire in the wild after a lightning strike or some event like that and then tending it for long periods, and manufacturing it.
Anyone who’s ever tried to use crude implements to actually manufacture fire would understand that there’s a great technologically leap and also maybe a mental leap that would have may have occurred a little later in our timeline.
Chris - Indeed. Someone who’s tried to make a fire in a camp the traditional way, it takes quite a bit of dedication, doesn’t it!
Lee - Extraordinary.
Chris then received this question from Sarah on Twitter...
Chris - Sarah Davey who wants to ask you, Owen, as a geologist, do you have a favourite rock?
Owen - I do. that rocks called a Blueschist and, as the name suggests, it’s a very vibrant, blue colour. Not only are they very attractive to look at in the field, they are also very special rocks because they tells us that there was an ancient subduction zone at that locality, so that’s where one plate goes underneath another.
Chris - What are they made of?
Owen - They’re made of principally a mineral called glaucophane [Na2(Mg3Al2)Si8O22(OH)2] and this has a very, very distinctive blue colour which gives it a very simple name, the blueschist.
Lee - I had a pet rock.
Chris - Go on…
Lee - Everyone who wants to get into geology has a pet rock when they’re a kid and so I had one. I lost it though and it’s been sad ever since.
Owen - Oh, your life could have turned out very differently.
Chris - Imagine what you could have been if you’d still got that pet rock today.
But what about dinosaurs?
Chris - Interestingly, Jason, because Lee’s saying about our ancient human ancestors losing their hair but what about dinosaurs? What were they covered in because if you go to museums and things you see many specimens of dinosaurs and they show things with skin a bit like a crocodile, but they’re not exclusively like that are they?
Jason - That’s actually a really interesting question and there’s a lot of research being done on this issue right now, and there's’ a lot of controversy. From certain parts of the geologic record you have particular environments where you find fossils that actually preserve the impressions of soft tissues. With certain dinosaur groups, when we find those impressions, they often include integumentary structure that look kind of like hair. They’re almost quill shaped and they’re often called “protofeathers” because they have kind of a feather like appearance to them.
So right now there’s a big question as to when do these protofeathers first show up in the history of dinosaurs? Is this a feature that all dinosaurs have primitively at the origin of the group, or is this something that’s evolved once or more than once very high up or higher up in these nested groups within dinosaurs? Certainly, by the time we get to true birds, things like archaeopteryx, then we see these well developed flight feathers and so we know what they’re covered with. But whether or not T. Rex, for example, Tyrannosaurus or any of the larger sets would have had an overall covering and integument or feather-like structures, it’s a little more poorly understood.
Amazingly for some animals like velociraptor, a small maniraptoran that’s risen to fame through the Jurassic Park films, we know they actually had probably elongate feathers running down the undersides of the arms because we’ve found specimens that have feather quill spots on the bone.
Chris - Do you think that the dinosaurs could have evolved to have feathers in order to conquer new patches of the Earth, to access new bits of the Earth which would have previously been a bit cold for them, and having feathers enabled them to access and use those areas? Because there’s populations of dinosaurs - and therefore competition went up in warmer spots - the choice spots were taken, so this enabled them to go into further reaches because it gave them insulation?
Jason - It’s possible, although the initial function for these feather-like structures is not 100% known. They may have functioned as insulation for the animals but also, where we find them on these well-preserved specimens, they’re actually quite patchy along the body, so they’re not presented on the animals as being a complete covering to keep them warm. These patchy distributions suggest that maybe what they were being used for was actually communication. That they could have had colour cells in them and they could have functioned as a form of display.