hominin | OpenSTEM Pty Ltd

What Makes Humans Different From Most Other Mammals?

Well, there are several things that makes us different from other mammals – although perhaps fewer than one might think. We are not unique in using tools, in fact we discover more animals that use tools all the time – even fish! We pride ourselves on being a “moral animal”, however fairness, reciprocity, empathy and cooperation have been demonstrated in apes and monkeys. Genetically we differ by only 1.09% from gorillas, 1.14% from chimpanzees, 2.46% from Old World monkeys and we share 50% of our DNA with bananas!

Recent research has demonstrated one of the ways that we are unique and this research is being used to help us to understand our human lineage, as well as giving us new insights into some diseases, such as cancer. The key to this discussion is a set of complex sugar chains (or carbohydrates), called glycans, which occur on the surface of cells. In particular, a glycan called Neu5Gc. It seems that at some point in the distant past, the malaria parasite used this glycan to anchor itself to the cells of primates and infect them with malaria, and human ancestors responded by losing the glycan, thus becoming immune to malaria. Unfortunately for us, a new type of malaria found a new glycan to attach itself to (this one is called Neu5Ac), which meant that humans could catch the new strain of malaria. This explains why humans are immune to the strains of malaria which affect great apes, such as chimpanzees, but are susceptible to strains of malaria which don’t affect the apes.

Humans became almost unique amongst mammals in not having the glycan Neu5Gc. It is thought that this mutation occurred between 2 and 3 million years ago and might have contributed to humans developing their own distinct lineage. Part of the glycan also becomes integrated as a molecule in bone, which gave researches hope that they might be able to find traces of the molecule from Neu5Gc in fossil bones. Whilst we have been successful in extracting ancient DNA from Neanderthal bones as old as 430,000 years and from horse bones as old as 700,000 years, fossils that are millions of years old have not been able to yield enough viable DNA using current techniques.

So researcher Ajit Varki, Distinguished Professor of Medicine and Cellular and Molecular Medicine at UC San Diego School of Medicine, started with 50,000 year old bones from a cave bear, from which they were able to extract the molecule. Varki then approached Maeve Leakey, Director of Field Research at the Turkana Basin Institute, who gave them a fragment of bone from a 4 million year old buffalo-like animal, found in the same layer as some hominin fossils. Once again the researchers were able to extract the molecule left in the bone by Nue5Gc. It is now hoped that they will be able to test fossil hominid bones in order to see which ones lacked Neu5Gc (and are thus likely to be our direct ancestors) and which ones had it.

Modern humans usually do have trace amounts of Neu5Gc, thought to enter our bodies from eating the meat of animals which have the glycan. Our bodies produce a slight immune response to the glycan, which might aggravate diseases such as cancer, opening new avenues for research and proving how research in one area of science, such as paleoanthropology, can have effects in other areas, such as medicine. It might therefore also be possible to see how much meat our ancestors included in their diets – always a controversial topic.

New Dates for Human Relative + ‘Explorer Classroom’ Resources

During September, National Geographic is featuring the excavations of Homo naledi at Rising Star Cave in South Africa in their Explorer Classroom, in tune with new discoveries and the publishing of dates for this enigmatic little hominid. A Teacher’s Guide and Resources are available and classes can log in to see live updates from the site. The material is also archived and can be watched via YouTube at a later date.

We’ve probably all heard of the little hominids from neighbouring Indonesia – Homo floresiensis and how they were initially dated to less than 50,000 years ago, which was then revised to between 60,000 and 190,000 years ago. These dates are still relatively recent for a hominid on the same general family tree as ourselves and reminds us all that there were several branches on this tree, of which ours is only one.

An interesting hominid was discovered in South Africa in 2014, named Homo naledi, this species was also relatively small and had a curious mix of features – some seeming very old (curved hands and fingers, well suited for climbing trees) and others looking more modern (legs suited to walking fully upright). Anthropologists and evolutionary biologists wondered where on the family tree these guys belonged – were they millions of years old, or more recent? The dating of the bones was an enormous challenge – partly because the deep cave where the fossils were found could only be accessed through an extremely narrow (20cm wide) gap in the rocks, and partly because the deposit lacked material that could be dated easily.

This year dates were published, obtained from a range of scientific techniques, including optically stimulated luminescence, Uranium-series and electron spin resonance dating (see OpenSTEM’s Absolute Dating Methods resource for explanations of some of these techniques). Both the sediments around the bones, as well as 3 fossil teeth were dated. The dates all clustered between 200,000 and 400,000 years ago. These dates are much more recent than was thought from analyses of the bones themselves. The dates are also contemporary with the very earliest of our own direct ancestors, implying that Homo naledi and our own ancestors shared the savannas of Africa hundreds of thousands of years ago. Yet another reminder of the diverse and complex nature of our family tree!

Am I a Neanderthal?

The whole question of how Neanderthals are related to us (modern humans) has been controversial ever since the first Neanderthal bones were found in Germany in the 19th century. Belonging to an elderly, arthritic individual (a good example of how well Neanderthals cared for each other in social groups), the bones were reconstructed to show a stooping individual, with a more ape-like gait, leading to Neanderthals being described as the “Missing Link” between apes and humans, and given the epithet “ape-man”.

Who were the Neanderthals?

Modern reconstruction – Smithsonian Museum of Natural History

Neanderthals lived in the lands surrounding the Mediterranean Sea, and as far east as the Altai Mountains in Central Asia, between about 250,000 and about 30,000 years ago. They were a form of ancient human with certain physical characteristics – many of which probably helped them cope with the cold of Ice Ages. Neanderthals evolved out of an earlier ancestor – Homo erectus, possibly through another species – Homo heidelbergensis. They had a larger brain than modern humans, but it was shaped slightly differently, with less development in the prefrontal cortex, which allows critical thinking and problem-solving, and larger development at the back of the skull, and in areas associated with memory in our brains. It is possible that Neanderthals had excellent memory, but poor analytical skills. They were probably not good at innovation – a skill which became vital as the Ice Age ended and the global climate warmed, sea levels rose and plant and animal habitats changed.

Neanderthals were stockier than modern humans, with shorter arms and legs, and probably stronger and all-round tougher. They had a larger rib cage, and probably bigger lungs, a bigger nose, larger eyes and little to no chin. Most of these adaptations would have helped them in Ice Age Europe and Asia – a more compact body stayed warmer more easily and was tough enough to cope with a harsh environment. Large lungs helped oxygenate the blood and there is evidence that they had more blood supply to the face – so probably had warm, ruddy cheeks. The large nose warmed up the air they breathed, before it reached their lungs, reducing the likelihood of contracting pneumonia. Neanderthals are known to have had the same range of hair colours as modern humans and fair skin, red hair and freckles may have been more common.

They made stone tools, especially those of the type called Mousterian, constructed simple dwellings and boats, made and used fire, including for cooking their food, and looked after each other in social groups. Evidence of skeletons with extensive injuries occurring well before death, shows that these individuals must have been cared for, not only whilst recovering from their injuries, but also afterwards, when they would probably not have been able to obtain food themselves. Whether or not Neanderthals intentionally buried their dead is an area of hot controversy. It was once thought that they buried their dead with flowers in the grave, but the pollen was found to have been introduced accidentally. However, claims of intentional burial are still debated from other sites.

What Happened to the Neanderthals?

Anatomically modern humans emerged from Africa about 100,000 years ago. Recent studies of human genetics suggests that modern humans had many episodes of mixing with various lineages of human ancestors around the planet. Modern humans moved into Asia and Europe during the Ice Age, expanding further as the Ice Age ended. Modern humans overlapped with Neanderthals for about 60,000 years, before the Neanderthals disappeared. It is thought that a combination of factors led to the decline of Neanderthals. Firstly, the arrival of modern humans, followed by the end of the Ice Age, brought about a series of challenges which Neanderthals might have been unable to adapt to, as quickly as necessary. Modern humans have more problem solving and innovation capability, which might have meant that they were able to out-compete Neanderthals in a changing environment. The longest held theory is that out ancestors wiped out the Neanderthals in the first genocide in (pre)history. A find of Neanderthals in a group, across a range of ages, some from the same family group, who all died at the same time, is one of the sites, which might support this theory, although we don’t actually know who (or what) killed the group. Cut marks on their bones show that they were killed by something using stone tools. Finally, there is more and more evidence of what are called “transitional specimens”. These are individuals who have physical characteristics of both groups, and must represent inter-breeding. An example is the 4 year old child from the site of Abrigo do Lagar Velho in Portugal, which seems to have a combination of modern and Neanderthal features. The discovery of Neanderthals genes in many modern people living today is also proof that we must have interbred with Neanderthals in the past. It is thought that the genes were mixed several times, in several parts of the world.

Am I a Neanderthal?

So how do we know if we have Neanderthals genes? Neanderthal genes have some physical characteristics, but also other attributes that we can’t see. In terms of physical characteristics, Neanderthal aspects to the skull include brow ridges (ridges of bone above the eyes, under the eyebrows); a bump on the back of the head – called an occipital chignon, or bun, because it looks like a ‘bun’ hairstyle, built into the bone; a long skull (like Captain Jean-Lu Picard from Star Trek – actor Patrick Stewart); a small, or non-existent chin; a large nose; a large jaw with lots of space for wisdom teeth; wide fingers and thumbs; thick, straight hair; large eyes; red hair, fair skin and freckles! The last may seem a little surprising, but it appears that the genes for these characteristics came from Neanderthals – who had a wide range of hair colours, fair skin and, occasionally, freckles. Increased blood flow to the face also would have given Neanderthals lovely rosy cheeks!

Less obvious characteristics include resistance to certain diseases – parts of our immune systems, especially with reference to European and Asian diseases; less positively, an increased risk of other diseases, such as type 2 diabetes. Certain genes linked to depression are present, but ‘switched off’ in Neanderthals. The way that these genes link to depression, and their role in the lifestyles of early people (where they may have had benefits that are no longer relevant) are future topics for research and may help us understand more about ourselves.

Neanderthals genes are present in modern populations from Europe, Asia, Northern Africa, Australia and Oceania. So, depending on which parts of the world our ancestry is from, we may have up to 4% of our genetics from long-dead Neanderthal ancestors!

New Research on Our Little Cousins to the North!

Last year, several research papers were published on the ongoing excavations and analysis of material from the island of Flores in Indonesia, where evidence of very small stature hominins was found in the cave of Liang Bua, in 2003. The initial dates dated these little people to between 50,000 and about 14,000 years ago, which would have meant that they lived side-by-side with anatomically modern humans in Indonesia, in the late Ice Age. The hominins, dubbed Homo floresiensis, after the island on which they were found, stood about 1m tall – smaller than any group of modern humans known. Their tiny size included a tiny brain – more in the range of 4 million year old Australopithecus than anything else. However, critical areas of higher order thinking in their brains were on par with modern humans.

Baffled by the seeming wealth of contradictions, these little people raised, researchers returned to the island, and the cave of Liang Bua, determined to check all of their findings in even more detail. Last year, they reported that they had in fact made some mistakes, the first time around. Very, very subtle changes in the sediments of the deposits, revealed that the Homo floresiensis bones belonged to some remnant older deposits, which had been eroded away in other parts of the cave, and replaced by much younger layers. Despite the samples for dating having been taken from close to the hominin bones, as luck would have it, they were all in the younger deposits! New dates, run on the actual sediments containing the bones, gave ages of between 190,000 to 60,000 years. Dates from close to the stone tools found with the hominins gave dates down to 50,000 years ago, but no later.

The researchers – demonstrating a high level of ethics and absolutely correct scientific procedure, published the amended stratigraphy and dates, showing how the errors had occurred. At another site, Mata Menge, they had also found some ancestral hominins – very similar in body type to the ones from Liang Bua, dated to 700,000 years ago. Palaeoanthropologists were able to find similarities linking these hominins to the early Homo erectus found on Java and dated to about 1.2 million years ago, leading researchers to suggest that Homo floresiensis was a parallel evolution to modern humans, out of early Homo erectus in Indonesia, making them a fairly distant cousin on the grand family tree.

Careful examination of the deposits has now also called in to question whether Homo floresiensis could control fire. We know that they made stone tools – of a type pretty much unchanged over more than 600,000 years, and they used these tools to help them hunt Stegodon – an Ice Age dwarf elephant, which was as small as 1.5m at the shoulder. However, researchers now think that evidence of controlled fire is only in layers associated with modern humans. It is this cross-over between Homo floresiensis and modern humans, arriving about 60,000 – 50,000 years ago, that is a focus of current research – including that of teams working there now. At the moment, it looks as if Homo floresiensis disappears at about the same time that modern humans arrive, which sadly, is a not totally unlikely pattern.

What does this have to do with Australia? Well, it’s always interesting to get information about our immediate neighbours and their history (and prehistory). But beyond that – we know that the ancestors of Aboriginal people (modern humans) were in Australia by about 60,000 – 50,000 years ago, so understanding how they arrived is part of understanding our own story. For more case studies on interesting topics in archaeology and palaeontology see our Archaeology Textbook resources for Year 11 students.

3D prints of early hominins: ergaster

homo-ergaster-front — Homo ergaster, KNM-ER 3733 (female, 1.8mln yrs old)

Meet Homo ergaster (also known as African Homo erectus), specifically specimen KNM-ER 3733.

How cool is this? We think very cool. This is the same fossil you see a photo of all over the net. It’s amazingly different when students can actually hold a print in their hands, and study it. And after that, you realise how unsatisfactory diagrams are.

This is a very old piece of our human (hominin) history. Our ladyfriend ergaster here (the skull is thought to be of a female) is one of the oldest of her kind ever found, and approx 1.8 million years old.

homo-ergaster-side — ergaster side view – you can see and feel the teeth!

Mind you, this particular print we did is only half-size (by X/Y/Z, not volume) but the detail is fantastic. On the second photo you can clearly see some teeth and yes you can actually feel them!

While the skull is fossilised and filled-in, the zygomatic arches on the side are still there (they’re missing in many specimens) and with the right slicer settings (including scaffolding) the printer has no problem creating a beautiful print. It just takes a while…

This skull print and some others have already been used by Claire Reeler (archaeologist) for a project at Grovely State School. The kids had a great time, an awesome hands-on learning experience, and we hope to publish the materials here soon so you can use them too.