Native American origin - A review

You might be surprised to learn that the peopling of the Americas (just in case you get confused I'm talking about North and South America throughout this post) occurred extremely late in the day compared to other continents. It wasn't until around 17,000 years ago that the first pioneers arrived, compared to Australia 50,000 ya and Europe 40,000 ya. The reason for this colonisation being so late in our history is due to the prior isolation of North and South America to the rest of the world. This isolation allowed many extraordinary species to evolve which are not found anywhere else including the megafaunal giant ground sloth, the saber tooth cat Smilodon and short faced bears, however it prevented Homo sapiens from entering.

Figure 1 Species endemic to the Amerias - Short faced bear, Smilodon and Giant ground sloths  

The theory generally accepted these days is that the entry route into the Americas was via the Bering Strait land bridge. This bridge was originally created during the last glacial maximum 26,000-19,000 ya a time when ice sheets were at their most extensive, but the bridge lasted right up until 11,000 ya. Over the course of many generations hunters would have migrated across the land bridge following herds of caribou from Siberia into Alaska, from here they followed the coast down the west of North America and eventually into South America, this route can be traced by an increasing decline in genetic diversity displayed by native populations as you travel south.

Figure 2 - humans migrated from Siberia into Alaska

Other theories which have been dismissed include entry to the Americas by South Asia and Polynesia on multiple occasions by means of the sea and by land. The land bridge theory was finally accepted as the most likely in 1997 thanks to genetic evidence linking the Siberian and Alaskan populations. However although the location of migration was agreed upon, the number of migrations which took place were still open for debate. The original 1997 study proposed that the whole population of the Americas stem from a single migration from East Asia.

A new paper coordinated by Professor Andres Ruiz-Linares of UCL and published in Nature in August of this year may shed some light into what really happened. Through more extensive evaluation of the genetics of both North American populations and Siberians they concluded that the migration actually occurred in three waves of migration. Although the first wave of migration did populate the majority of the two continents, some Arctic populations trace their heritage back to a second and third migration occurring later in history. The study also highlights how complex dispersal patterns can be; some Central American populations are equally related to both North and South American populations, suggesting that some back migration would have occurred (people travelling from South to North America). This kind of migration pattern can muddy the waters and make it confusing to see the real picture.

Figure 3 - The new three wave migration route

For the time being the new 2012 paper seems to be accepted by the scientific community as the most likely scenario,  however it should be remembered that studies such as these contain limitations. In this case it is a lack in genetic data, due in part to a reluctance among native populations to partake in the study but also to uncertainty whether skeletal remains are ancestors of tribes or not. I think it will be interesting to see whether scientists manage to obtain more data in future and if so what new evidence may emerge on the settling of the Americas, there may have been many more migrations yet to be discovered.

Out of Africa 2 - Homo sapien dispersal - a review

We've now learnt that all human beings today can trace their origin back to Africa, so now I bet you're wondering about how this second Out of Africa dispersal played out.

Today we have wind back 200,000 years ago (ya), our location is East Africa. Over a million years have past since Homo erectus successfully migrated, and they have now set up home throughout Asia and Europe. The earliest known remains of H. sapien are found in Ethiopia 160,000ya. From this singular east African origin, three lines diverged, one travelling to southern Africa, one to Central and West Africa, and the last line traveled North. It is this last lineage we are interested as this small group are the ancestors of every non African person in the World. 

Figure 1 The range of other Hominid groups and our dispersal route.
1 = H. sapien
2 = Neanderthal
3 = H. erectus

The most widely supported route these early H. sapiens took is strikingly similar to the H. erectus dispersal I described in Out of Africa 1 - Homo erectus dispersal - climate induced changes in sea level enabled a crossing of the red sea and into the Arabian peninsular.  Ericksson's 2011 paper lends support to the importance of climate in facilitating the migration, he explains that '60-70kya (thousand years ago) the global colonisation of humans ancestral to modern populations was prevented by the arid climate in Northern Africa and much of the Arabian peninsular.' Long after spreading throughout Asia they traveled North into Europe, following game migrations and favorable climates. 

Upon reaching the China region 70,000ya there was a divergence. It seems one group island hopped through Indonesia, eventually entering Australia 50,000ya; whilst another group dispersed Northwards, crossing into the Americas 15,000ya. 

An opposing view is presented in  Rasmussen et al.  2011 paper. They used DNA analysis of an aborigine’s lock of hair and discovered a greater similarity to African DNA compared to Asian and European. These findings go against the idea that a single migration occurred and that the Australian population diverged from the Asian one. Instead it suggests that the ancestors of the Australian population left Africa first 75,000ya, travelling along the South Asian coast and interbreeding with the Denisovian population before arriving in Australia. The evidence of these travels would then have been swallowed up by rising sea levels; the Asian and Europeans would then have emerged from Africa separately at a later date around 25,000-38-000ya. The main archaeological evidence to back up this theory comes from the 'Mungo man'a 50,000ya skeleton found in Australia. the path this early migration may have taken has not preserved and so there is minimal physical evidence however new technique of matching DNA to powerful computer models is reputed to make up for this; however the research is still very new and it will be interesting to see if it stands up to academic scrutiny over the coming years. 

Alternative dispersal routes

A bit of fun...

Hey folks, here's some light relief with a human evolution game. Let's see if my blog has taught you a few things. All topics the game covers are mentioned in the 'Walking with Cavemen' series that I linked you a few weeks ago.

Enjoy.

Timings - a review

I'm sure many of you reading this are aware of the magazine New Scientist. It covers stories which are newly emerging and occasionally controversial; in last weeks issue (24th November) they ran a story which suggested that we have been miscalculating the age of our split with the last common ancestor of chimpanzees; a result which would mean the re-writing of textbooks and a shift in the way we view our evolution. Pretty revolutionary stuff right? That's what I thought; lets take a look at the evidence.

The way we have always been told in schools and lectures is that the timing of the split between us and chimpanzess was 5 million years ago. This age was a fork in the evolutionary road, along one branch an ancestor evolved into modern day chimpanzee, along another the ancestor became us. The technique of working out this date lies in our DNA; with each generation new mutations appear, these occur randomly and many do not cause any significant changes affecting our likelihood to survive, they just sit there hanging out and can be picked up upon DNA analysis. The rate these mutations accumulate remains relatively stable through the generations and was thought to be 75 per generation, this allows us to calculate how many generations there have been since our ancestors split with the chimp's ancestors, all we have to do is add up the mutations.

Sounds pretty simple, however a recent study by Kong et al. proves that this method needs some corrections. His study was focused on mutations observed between human parents and offspring, after analysing the genetics of 78 'parent offspring trios' (child with both parents) they found that each child had on average 36 mutations which  were new and not shared with either parent. This is clearly half what we have always thought; the mutations accumulate much more slowly Now if we add up all the mutations it appears that the acutal age of split between us and chimps is more like 7-13 million years.

Figure 1 Old 5my split versus the newer estimates of 7-13my

If this more ancient split is to be believed then Australopithicus afarensis may not be the oldest ancestor we can identify as hominin, other species may have to be brought into the family such as Sahelanthropus tchadensis at 6-7mya and Orrorin tugenensis at 6mya .Other ramifications include an older Homo sapien migration out of Africa date at around 90,000-130,000 years ago (a topic I haven't covered yet but when I do I will try to give a scenario based on both dates).

All of this is enough to get very excited, Kong's paper was published in August of this year (2012) in Nature, a journal which undergoes heavy peer reviewing, something which helps with the reliability of a paper. However some anthropologists in the field such as Matt Skinner from UCL, suggest caution should be used when reading such revolutionary claims. Public interest is focused on the more sensationalist stories and scientists are therefore pressured into making claims they themselves would rather not make in order to get their articles to be published. Whether or not this is the case with this story is up for debate and I'd be interested in hearing your opinions.

Oh dear....

Trawling through the internet this evening I stumbled across this article. From real scientific theories to hilarious claims of sequencing Bigfoot DNA. This is the kind of thing to really not fall for (unless you're having a very silly moment)!

The geographic review of Homo sapien - An update!

This post is a follow on to the review posted on Friday the 9th of November (you might want to brush up a bit before you read on so I don't leave you behind). In our first look into where on earth our species comes from I took you on a tour through the groundbreaking primary papers which first furnished the theories with scientific evidence. However as is always the case with science, things move on rapidly; new research comes out all the time, slowly allowing us to sift out all the falsities thereby allowing the thousands of year old tale to be told.

When I last left you it was with the notion that the best supported view of the scientific community was that of the Out of Africa hypothesis. The Multiregional theory being blown out of the water by mitochondrial DNA evidence. However new research muddies this clear distinction (things in science are never as simple as they seem).

Recent scientific advancements now allow us to sequence the genomes of the most recent species of Hominin we shared the world with. These include the Neanderthals and the Denisovians. The results of these studies were published by Green et al. and Reich et al. respectively in 2010. The findings of which are discussed by Svante Paabo in the video below.

The Out of Africa hypothesis is defined as a total replacement of the local populations by Homo sapien with NO interbreeding, whereas the Multiregional hypothesis proposes an independent evolution of modern from indigenous Hominin species. The new research suggests a compromise between the two extremes; H.sapiens did emerge from Africa to conquer the world but they got jiggy with the locals too, and in doing so enabled the preservation of an extinct species to live on in us today .

Figure 1 H. sapien falls for a Neanderthal

This all seems fine and dandy, however calculating these findings is error prone. From information gained in previous molecular biology modules I understand there to be many complexities and problems encountered sequencing ancient DNA; in some instances the DNA is contaminated and the strands being sequenced are in actual fact the genetic material of the researcher. The two studies mentioned above have undergone rigorous peer reviewing and therefore the results are much more reliable, for the time being it is to be believed that Europeans share 1-4% of DNA with Neanderthal man and Melanesians share 4-6% of DNA with Denisovans; the question is how Neanderthal are you?

Climate's role in Out of Africa 1

So now we've explored the route the first adventures took, lets take a closer look at what was going on with the climate. The reason why I'm devoting a blog post on this topic is that the changes in climate in the time period 1.8-2 ma (million years ago)  was one of the main factors enabling this migration of Homo erectus to occur.

The epoch we are looking at is the Pleistocene, it lasted from approximately 2.6 ma until 11,000 years ago and is characterised by a climate which fluctuated between cold glacial to warmer inter glacial periods. As the world slipped into a glacial period, huge ice sheets would descend from the poles and drape themselves across the Northern Hemisphere, locking away massive quantities of fresh water in the process.

Figure 1 Although it doesn't go right back to the period we're looking at this graph gives you an idea of the shifting climate occurring in the Pleistocene

Prior to the Pleistocene the climate had been relatively stable; in Africa grass lands were dominant and the rainforests had receded. It is interesting to note that this change can be determined by looking at the type of carbon that has been stored by the plants - C4 grasses are more dominant in arid environments and C3 leaves and plants prefer warm wet conditions. We use carbon dating amongst other methods to create a picture of the palaeoenvironment.

So anyway, the stage was now set for migration: resources were becoming scarcer, resulting in groups of Hominins having to travel further for their meals. There was only one problem - there was no way out of Africa. This all changed with the arrival of the glacial periods; the formation of ice requires large quantities of water, water which was sourced from the oceans. So much water was taken to form these ice sheets that sea level dropped by around 100m, opening up land bridges and allowing species to cross continents. In our case this land bridge was the Levantine corridor in Israel. Once H. erectus were across this land bridge they could spread onwards to conquour the rest of Asia and eventually a very chilly Europe.

Figure 2 Hominins in Europe

Video Time 2

Hey guys thought I'd take a break from all the serious long posts by giving you a bit of light relief in video form.

If you haven't heard of it before The Incredible Human Journey is great! Skip to episode 2 for a thorough analysis of the Multiregional vs Out of Africa debate I was explaining in a previous post.

Out of Africa 1 - Homo erectus dispersal

When reading my last blog post on the geographic origin of Homo sapiens it may have surprised you to learn that our own species was not the first to venture out of the motherland and into unchartered territories. The first colonisation was actually achieved over a million years before our H. sapiens had even evolved. This ancient species began as H. ergaster and became H. eretus

The origin and dispersal of these species is still much debated (anthropologists never seem to agree on anything!), but I will take you on the journey that is most widely accepted. If you are interested in other theories then please comment below and we can examine the debate in detail.

The setting today is Eastern Africa 1.8 million years ago – the home of H. ergaster. This species possessed a larger brain than its predecessor H. habilis, and was likely fully bipedal; the remains of this species is almost entirely found in the African continent. However it seems these apemen were not content in their home land as a small band managed to migrate north across a grassy Sahara and across the Levantine corridor into Israel. It is in this region of the world that we think the speciation into H.erectus occured as speciemens have been found in Dmanisi Georgia. This new species was the most advanced Hominin yet and had many similarities to us. However there was one very noticeable difference - these guys had HUGE brow ridges; the purpose of which is still unknown.

Take a look at those brow ridges! Fig 1

 Their journey continued from here, over the next few 100,000 years they spread across Asia and into Europe; we know this by analysing remains which have been found in S.E Asia 1.6ma and Spain 1.1ma.

The route taken by H. erectus Fig 2

To be able to master the multitude of ecosystems that must have encountered along their epic journey across the Old World they must have been highly adaptable and extremely hardy. Their success may be owed to their advanced stone tools made with Archeulean technology and their highly meat orientated diet, allowing enough energy to fuel a big brain. Interestingly none of these tools are found east of India, a cut-off named the Movius Line. However in my opinion this is due to H. erectus's adaption to utilising local materials such as bamboo to make tools.

I hope you’ve learned something in this post, next time we’ll examine how climate enabled this migration to take place. 

The geographic origin of Homo sapien. A review

As promised this post will be another literary review of key papers which shape our understanding of human origins. Today we are going to examine opposing theories which attempt to explain how our species Homo sapien developed from the ancestral condition.

First let us paint a picture of the time period we are examining. It is 200,000 years ago; different species of the genus Homo are already dispersed all over the Old World (Africa, Asia and Europe): with H. erectus in Asia and Neanderthals in Europe. The climate is fluctuating between cold glacial and warmer interglacial periods and mega fauna dominate. This is the time where Homo sapiens make their debut appearance. Papers propose differing views of how this development into modern man came about; did H. sapiens evolve in Africa and replace all existing Homo species, or did they arise independently from pre existing local populations?

Anthropologist Allen Wilson was a proponent of the former view, the ‘Out of Africa’ hypothesis. In his 1987 paper he provides supporting evidence by analysing the mitochondrial DNA of different human populations from around the world. I realise many of you may not know what mitochondrial DNA is so I will give you a brief description: mitochondria exist in every cell in your body; they were once bacteria and act as oxygen factories. Mitochondria have a genome separate to the nuclear genome (chromosomes) we all know and love.  The brilliant thing about the mitochondrial genome is that they do not recombine like our chromosomes and instead passes intact directly from mother to offspring.  This allows the mitochondrial genome to be tracked back in time! Wilson chose 5 different populations from around the world: Africans, aboriginal Australians, Caucasians, Asians and aboriginal New Guineans and used their mitochondrial DNA to produce a restriction map. This map identifies the mutations which have occurred in each lineage, and upon comparison to one another can ultimately show where and when the original ancestor of all lineages existed. The conclusions made by Wilson are that this Eve of humanity existed about 200,000 years ago in Africa.

The consequence of this conclusion is that Homo sapiens must have evolved in Africa before spreading fully formed (with a brain size identical to our own) to colonise the rest of the world. Any species they may have met on their travels be it H. erectus or Neanderthals would have been outcompeted and driven to extinction.

Figure 1 A diagram of the two theories

The suggestions made by Wilson’s paper were controversial and were quickly attacked by proponents of a multi regional human evolution. A paper by Thorne and Wolpoff in 1992 argued that the methods used to calculate the 200,000 year old date of divergence was inaccurate. They suggested that the date of divergence of these 5 human populations should have actually been 1 million years ago. If this were true then the scenario would be very different: the original ancestor would have been much more primitive with a smaller brain size, each different regional population would have developed into a modern human separately and in situ. In Asia H. erectus would have developed into modern Asians and In Europe H. erectus would have developed into Neanderthals and then into modern Europeans; with interbreeding happening along the way.

Although this idea does seem quite outlandish Thorne and Wolpoff do provide some good evidence; the technology and culture of modern humans in Europe were identical to the Neanderthals they lived alongside including their burial systems and butchering of game. If Wilson’s idea were correct then it would be expected that the hand axe technologies of the African Eve population would spread alongside their population, however no hand axes are found outside of Africa. These two examples show that either the Out of Africa theory is incorrect or that the modern humans leaving Africa adapted to local practices and given up any former technology they had developed. 

Another important disparity discussed by Thorne ad Wolpoff’s paper is the lack of African cranial features found in Asia and Europe. Instead certain diagnostic characteristics of populations continue right up until the present day. Although the paper includes many examples, the best one comes from examination of Chinese fossils. The unique feature of a shovel like maxillary incisor is shared by both ancient specimens and the modern population of China; supporting an in situ transition from ancient to modern local population and not a replacement.

All of the evidence provided by the multi regional hypothesis is quite convincing, however the majority of the scientific community still support the Out of Africa theory. I believe this is mainly due to the lack of substantial fossil evidence to really support Thorne and Wolpoff’s claims. On top of this using mitochondrial DNA  to calibrate an ancestors age is a method approved by many to be accurate enough to use as evidence, and therefore the claim that Wilson’s method is inaccurate does not stand up to scrutiny. As is usually the case in a scientific debate more evidence is required to determine which paper is valid but I hope you have gained enough information from this review to form your own opinion on this topic.  

This review has been about the classic papers, for a more up to date analysis check out my updated version (30th November)..

References

Thorne, A.G., and Wolpoff, M.H., 1992. The Multiregional Evolution of Humans. Scientific American. 266(4) pp. 28-33.

Cann, R.L., Stoneking, M., and Wilson, A.C., 1987. Mitochondrial DNA and human evolution. Nature. 325(1) pp. 31-36.

Amazing summary!

This is a fantastic summary of everything mentioned so far, the guy presenting it is incredibly engaging, if you're interested in sciencey stuff I recommend you watch more of his videos.

Also another review is being posted in the next couple of days, so come back again soon!

I've just been reading an interesting article on the BBC website published last year. It suggests that human origins can be traced back to southern Africa using studies of genetic variation. You can view it here; let me know your views on it!

The origin of bipedalism. A review

Becoming bipedal was a vital step in the path to humanity. Walking on two legs freed the hands of our ancestors enabling the crafting of tools, allowing a meat focused diet and ultimately leading to a bigger brain - the characteristic that has allowed us to become the dominant species we are today. We are the only mammal adapted to a life of walking upright; it is true that some Great apes do take to two legs but their bodies are not built for sustained periods of walking and they quickly revert to their more energy efficient movements.  

The transition to become a habitual 'upright ape' has not been an easy one; a variety of skeletal and muscular modifications were necessary to make bipedalism worthwhile, leading to back problems, hernias and extremely difficult child birth. So what factors would have made it necessary to leave a quadrupedal lifestyle which suited our ancestors for millennia?

The oldest and most well known theory to answer this question is the 'savanna hypothesis', suggested by Raymond Dart (1925). His idea being that bipedalism evolved in an open grassland setting, an environment created from receding rainforests.  It was here that ‘mammalian competition’ and lack of water provided the selection pressures required for an ape that relied on fast legs and a large brain to survive. At the time the hypothesis was proposed the earliest bipedal hominid – the Taung child was dated at 2.5 million years old (mya) (Dart 1925), ice core samples support a reduction in rainforest. They reveal that the climate at this time was indeed becoming cooler and dryer – a repercussion from the closing of the Panama seaway.

A classic image of early man in a savanna setting

A supporting hypothesis was put forward by Wheeler (1991), he proposed that walking upright would have allowed our ancestors to keep cool on the savanna due to a reduced surface area being exposed to direct sunshine and increased wind speeds away from the ground. These hypotheses seem simple and logical, however the discovery of the 4.4mya bipedal hominid –Ardipithecus ramidus pushes the origin of bipedalism back to a time when Africa was covered in thick rainforest; a finding which prompted scientists to seek new explanations.

A paper by Kevin Hunt (1996) gives a good alternative theory. It suggests that our ancestors developed their bipedalism whilst still in the trees; the idea was developed from an observational study of our closest living relatives – the Chimpanzee. These Great Apes use facultative standing to reach food items, holding onto overhead branches for support; Hunt argues that our early ancestors would have used a bipedal posture to attain food and this would have developed into efficient locomotion at a later point.

Modern Orangutans also use facultative standing to reach food items   

Unlike the Savannah hypothesis the postural feeding theory fits in with the rainforest environment that is predicted to have been present at the dawn of bipedalism, and is therefore in my opinion much more likely to be true. Other theories have also been put forward including bipedalism adapting to make sex organs more visible or to allow males to provide for their mates. The argument over which factor is the most likely is still ongoing, and this debate will be continued as new research emerges.

New research into this topic have put forward some new ideas, a 2011 paper by David Carrier proposes that sexual selection may have played a role. This is the selection of traits based on female preference rather than traits which will enhance survival, a bipedal stance would have enabled males to fight one another more effectively to gain mating rights to a female. Only males winning these fights would pass on their genes and therefore this gait would have been selected for.

Finally, a 2010 review of all bipedal hypotheses, concludes that no one hypothesis can explain our adaption towards a bipedal lifestyle, the issue is far more complex than that, an opinion I tend to agree with.

References

Dart, R.A., 1925. Australopithecus africanus: The man ape of South Africa. Nature, 115, pp.195–199.

Hunt, K.D., 1996. An ecological model for the evolution of bipedalism. South African Journal of Science, 92(2), pp.77-90.

Wheeler, P.E., 1991.The thermoregulatory advantages of hominid bipedalism in open equatorial environments: the contribution of increased convective heat loss and cutaneous evaporative cooling. Journal of Human Evolution, 21(2), pp.107-115.

Video time!

If you have a spare few hours here and there the series 'Walking with Cavemen' gives an entertaining narrative of human evolution. Although it glosses over some of the major debates in Palaeoanthropology it brings the world of these species to life, and Robert Winston's facial expressions are pretty hilarious too!

As the video isn't from youtube it won't let me embed them, but follow the links below for the episodes:

Episode 1 - Australopithecus afarensis

Episode 2 - Homo habilis/ Paranthropus boisei

Episode 3 - Homo erectus/ Homo ergaster

Episode 4 - Homo neanderthalis

The Genus part 2

At a similar time to Homo ergaster appearing in the fossil record, a  species called Homo erectus existed in Asia. Many people in the scientific community believe that these two species are interlinked and that H. erectus is just an Asian version of H. ergaster which migrated from Africa to colonise other climes. An alternative view is that H. erectus evolved completely separately in Asia and then migrated to Africa at a later date. An analysis will be conducted on this subject in a separate post so we can look at it in a bit more detail.

For now we'll push on with the biographies of the most influential species from our past.

H. erectus were a species of Homo who travelled a lot (assuming they evolved in Africa). In the 1.5 million years (around about) that they existed they managed to reach countries as far flung as China, India and Europe, surviving as hunter gatherers. Their brains were the largest to date at about 2/3 the size of ours, they were using this extra brain power for innovations such as ocean crossing by raft and controlling fire (although this is still a source of contention).

A trailer for the film 'Homo erectus'. Don't let the title fool you, this is a truly terrible film!

 

  Another species which has been found outside of Africa is that of Homo neanderthalansis; you may know them as neanderthals. In popular media this group has been described as the quintessential 'caveman' complete with bone club and a tiny intellect, however what you may not know is that they had brains actually larger than our own. Their morphology (structure) was more robust and muscly than ours and was evidently geared towards a life in cooler climes - a reflection of their commonly ice age habitat. Genetically neanderthals were very similar to us, so much so that there is debate about whether they should actually be a sub species of sapien instead of a seperate species all together. This would result in a reclassification of their name to Homo sapien neanderthalansis. They would have inhabited Europe 230,000 years ago until their extinction as recently as 28,000 years ago.  

Now, finally, we have reached the conclusion of our Homo safari, with a description of our own species Homo sapien. The earliest remains currently place the dawn of our species at 195,000 years ago, not too long after neanderthals; this was marked by a brain size equal to modern man and small teeth adapted for a varied diet.We quickly dispersed from Africa, travelling to Asia Europe and later the Americas and Australia, by 12,000 years ago we inhabited all continents except Antartica.

 

From left. H.erectus, H. neanderthalansis and H. Sapien.

The Genus part 1

Our species Homo sapien was not the only upright ape to develop in Africa, so far around 13 different species belonging to the genus Homo have been discovered (although this number is still debated). The characteristics which link them to one another are complex and would take up more space than this one post, I will therefore be mainly mentioning what is thought of as the key developments: an increasing brain size and a reduction in size of teeth. Bipedalism, which many people suggest was the biggest development in making us who we are today, was actually adopted by an even earlier ancestor 4 mya (million years ago) - Australopithicus.

Australopithecines were a genus of ‘upright apes’ and would have had a brain size similar to that of the Chimpanzee and teeth which were still much larger than our more recent ancestors due to their mainly vegetarian diet. They were living in eastern Africa until around 1.8 mya.

Next on the scene were Homo habilis 2.4 mya, this species is widely agreed to be the first true Homo and is notable for its increased brain size and a regular use of stone tools, there is also evidence of an increasing meat orientated diet, a change which would have helped boost brain size.

Homo ergaster was another important species to have developed, they were one of our direct ancestors and lived in southern and eastern Africa from 1.8 until 1.3 mya. They show modifications in gait which suggested a more upright posture and the development of running. This change would have allowed them to become more efficient hunters, extra resources which in my opinion could have boosted population numbers from an increase in numbers of offspring able to be supported. It has been put forward that H. ergaster may have migrated from Africa 1.75 million years ago, a topic hotly contested which will be discussed more fully in a later post.

From left to right - an Australopithecine, H. Habilis and H. ergaster

A Cladogram of the species mentioned:

http://throughevolution.files.wordpress.com/2011/09/hominina-cladogram31.jpg

For a more succinct view of the sequence of events check out this time line.

Next time will be the conclusion of 'The Genus'.

Beginnings

Hey Everyone,

As I'm sure you are aware, humans are everywhere! There is just no escaping them, we have spread to colonise almost every habitat on Earth. We have adapted the environment to suit our own purposes and increased in number to become the dominant life form on Earth. All of this from a small group of individuals which dispersed from Africa  around 1.7 million years ago. This blog is going to look at how the genus Homo accomplished this impressive feat. It will also look at the role climate has had in helping and hindering this journey and shaping the different ethnic groups we see today.

So buckle up and prepare yourself for an epic journey back to an age of Mammoths, Saber-toothed cats and giant Ground Sloths. We will visit ice ages and Sahara grasslands, examining the climatic shifts along the way. In this blog I hope to not just examine scientific papers but also bring you relevant videos and pictures which I have found interesting.

A Woolly Mammoth - painted by the people who hunted them

Hope you enjoy it!