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The Origin of Humans
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Human Evolution
In this course, Professor Matthew Cobb (University of Manchester) walks us through the history of how the modern human came to be. The modern version of the human was no more than a smart ape when it first appeared 50-60,000 years ago, but where did it come from, and what happened to it in its early stages? We begin by: (i) investigating the theory of evolution by natural selection and apply it to human evolution, looking at where they came from; before (ii) challenging common misconceptions of the Neanderthal and then examine their interactions with humans in their ~5,000 year overlap, as well as introducing the Denisovans; which follows into (iii) a more detailed description of the discovery of Denisovans, what they might have looked like and how they might have behaved; before finally (iv) taking a closer look at the marks our ancestors made on the world in the form of illustrations, drawings, and handprints on prehistoric cave paintings.
The Origin of Humans
In the first mini-lecture, we begin by appreciating the history of human evolution. To do so, we cover Darwin’s theory of evolution by natural selection, and the three parameters that determine whether a species will evolve over time. The evolution of humans to the modern version we know today is a complex story intertwined with closely related species, and in this lecture we begin to understand where it all began for the modern human. We start by tracing the first steps of humanity across the globe, originating in Africa, and discuss some of the incredible things we have learned about our history, including how humans became endangered by some major event.
Hello
00:00:05and professor Matthew Cobb at the University of Manchester.
00:00:07And in this mini lecture series, we're going to be looking at human evolution,
00:00:11how it took place
00:00:15and some of the most astonishing discoveries we've made over the last decade,
00:00:18which have utterly transformed our view of what it is to be human.
00:00:22Now the first question people want to know is, well, how did we come about?
00:00:28How did we appear?
00:00:34Very simple answer.
00:00:36But it needs a bit of explaining is through evolution by natural selection.
00:00:37Now this idea was first put forward by Charles Darwin
00:00:44in the 19th century,
00:00:47and it is very, very simple.
00:00:49Natural selection
00:00:52occurs when you have three conditions.
00:00:54Firstly, heritable characters. That is
00:00:59something that can be transmitted because it's
00:01:03got a genetic basis down the generations.
00:01:06Secondly,
00:01:10differences between individuals so you can't get evolution by natural selection.
00:01:11If there's no variability, variation is essential.
00:01:18So if you have a heritable character that is different
00:01:22between individuals and which leads to what's called differential fitness,
00:01:27fitness can be seen as survival, the ability to reproduce.
00:01:33If individuals with those different characters have
00:01:38different survivals or different abilities to reproduce,
00:01:42then you get a change in the genetic frequencies from one generation to another,
00:01:46and that is all evolution is. Evolution is a change in gene frequencies.
00:01:53A natural selection is this sifting of characters because they
00:01:58are associated with increased survival or ability to reproduce.
00:02:03And that over the vast depths of geological time produces changes
00:02:09and produces all the astonishing world we have around us.
00:02:16We have to remember
00:02:20there's no aim, no objective to evolution. We are not the point of it all.
00:02:21We are not the high point of evolution.
00:02:28Evolution by natural selection simply occurs where
00:02:31these three characteristics exist in whatever system,
00:02:36potentially on other worlds.
00:02:40If they have these three characteristics,
00:02:42then
00:02:45they will get evolution by natural selection to
00:02:46now. How does it apply to humans?
00:02:50Well, first thing we got to remember is in terms of talking about species,
00:02:53that a species from a biologist point of view is a group of organisms,
00:02:58a population that does not interbreed with another group.
00:03:04So, for example, we and chimpanzees are isolated.
00:03:09We, if we can't mate we can't produce fertile, can produce any offspring,
00:03:14the mind fertile offspring.
00:03:20Sometimes you get matings that occur,
00:03:23say between a horse and a donkey produces a mule,
00:03:25but they're still species because the mule is sterile.
00:03:28So if you can produce fertile speed, fertile hybrids, when you mate, then you are,
00:03:33by definition, part of the same species.
00:03:40If you can't,
00:03:43then your separate species
00:03:45and species appear primarily.
00:03:46They emerge because a population of organisms become separated,
00:03:49say, because of geological activity
00:03:54one they live on now, two sides of a river that has appeared.
00:03:56They can't. They're not birds.
00:04:01If their land mammals, for example,
00:04:03they can't get from one side of the river to the other,
00:04:04and you end up with two different species.
00:04:07You can see this, for example, in the Grand Canyon
00:04:09in America,
00:04:12where you get different species of land mammal on either side of the canyon,
00:04:13but the same species of bird which can clearly get over this obstacle. So isolation.
00:04:18Random evolutionary geological events
00:04:23produces different species over the depths of geological times,
00:04:27so
00:04:33to emphasis, we are not the point
00:04:34of three billion years of history of life on earth.
00:04:37We're just one particular, very smart ape that has appeared
00:04:40in the last few 100,000 years.
00:04:45and all
00:04:49of our molecular fossil genetic data
00:04:50underline the truth of this.
00:04:56Everything we know
00:04:58about the natural world about our place in it is
00:05:00reinforced by these discoveries which we're making every day.
00:05:04So the our world view has been changed in ways that you will see.
00:05:08It is all congruent with our genetic understanding of
00:05:13the d. N A. That is in all of us.
00:05:19The evidence I'm going to be presenting to you today is all about the genetic data.
00:05:22And sometimes students can find this a
00:05:30bit upsetting because it contradicts their beliefs.
00:05:35But
00:05:39I think you've got to realise, if you're a scientist,
00:05:40you can have whatever beliefs you want.
00:05:42That's fine.
00:05:44But you can't use your beliefs to decide
00:05:45what evidence you accept and what you reject.
00:05:49The data are the data,
00:05:52and that's what drives our views.
00:05:55And over the last decade,
00:05:58as we're gonna see D n A in particular ancient D N
00:06:00a DNA from extinct groups has changed our understanding of human evolution.
00:06:05So where do we come from? Well, the very short answer is Africa.
00:06:13We all come from Africa. All humans today can trace their origins back to Africa.
00:06:17We know this from the DNA that we can
00:06:24sequence from people around the world and our population.
00:06:26Genetics models show that they all converge.
00:06:30Every genome of every human that's alive today converges back in Africa
00:06:33around about 77,000 years ago. All humans lived in Africa.
00:06:38It appears that we originated around about 300,000 years ago.
00:06:45That's the latest fossil data.
00:06:50We now suspect that perhaps we left Africa in a number of waves, perhaps earliest,
00:06:53about 200,000 years ago.
00:06:59Recent re dating of some fossils found in
00:07:01Greece suggests that they were actual modern humans.
00:07:04But if we did leave Africa before 70,000 years ago,
00:07:08those humans died out because every human alive today
00:07:13can trace their origins back to Africa around about 70,000 years ago, that is.
00:07:19When we began,
00:07:23some of us began to leave Africa to disperse out to the rest of the world.
00:07:25So it seems that perhaps there were many movements out of Africa, not just one.
00:07:30Perhaps climate change may have driven people to start to move very, very slowly.
00:07:35Doesn't think that these were great treks or dispersant expeditions.
00:07:40This is slow movement around the planet,
00:07:45and the one at about 70,000 years ago is the one
00:07:48that led to all of us who are alive today.
00:07:51So it's not a colonisation by brave expeditions. It is simply slowly moving
00:07:54around the planet.
00:08:02And all this is supported by our genetics and by our fossil evidence.
00:08:04And we can do. We can see that, in fact, to get out of Africa.
00:08:09This map shows you simply by walking and occasionally getting in boats say,
00:08:12to get to Australia.
00:08:17By moving about one kilometre a year, you can spread around the planet.
00:08:18That's all you need to do. You're not trying to get to anywhere.
00:08:23You don't know where anywhere is you just a group of
00:08:26hunter gatherers slowly moving around the popular around the planet.
00:08:29We now know there's a lot of dispute about when we got to the Americas.
00:08:34Uh, and how we got there?
00:08:39Did we go up around the top, uh, through the frozen wastes of Alaska?
00:08:41Or did we go by boats via a coastal route?
00:08:46Recent footprints have been discovered in New Mexico.
00:08:49That suggests perhaps we got there a bit
00:08:52earlier than normally thought maybe 20,000 years ago,
00:08:55but basically
00:08:58that's how we got around the planet. We walked, and occasionally we got on boats.
00:08:59We can see this in our genes.
00:09:04This is one of my favourite graphs in the whole of biology.
00:09:07In general,
00:09:10biology doesn't do straight lines because biology
00:09:11is complicated straight lines for physics.
00:09:15But in this case, we've got a lovely straight line.
00:09:17This is showing the hetero cigar city that is the genetic variability of different
00:09:20indigenous peoples around the world,
00:09:26and you can see that it's declining with distance from Africa.
00:09:29So the
00:09:33greatest variability is in Africa, which is what you'd expect.
00:09:35That's where we come from our ancestral population.
00:09:39They have the largest amount of variability,
00:09:43and the smallest amount of variability is that in the most distant populations,
00:09:45those in the Pacific oceans.
00:09:51And you can imagine why, because you'll have had a
00:09:53large amount of variation, and then a sub group of that population moved away.
00:09:57So you've got less variation, and then a subgroup of that,
00:10:02and then a subgroup of that.
00:10:06So at each stage as we've moved, we've gradually reduced genetic variability.
00:10:07Finally, we can see
00:10:14that our existence. Our very existence is incredibly lucky.
00:10:16This figure is taken from six genomes, whole genomes of industry,
00:10:21of indigenous peoples.
00:10:25And what it shows us is that around about
00:10:2870,000 years ago,
00:10:32there was what's called a bottleneck a reduction
00:10:34in the size of the human population
00:10:37to around about 12,000 people.
00:10:40That's all there were
00:10:43in Africa, just 12,000 people. That's the arrow you can see on this figure.
00:10:46And it doesn't take much to imagine that disease or famine.
00:10:51Who knows what could have absolutely wiped us out 12,000 animals today.
00:10:55You had that in a wild population, you'd be quite concerned about its future,
00:11:02so humans are incredibly lucky.
00:11:07
Cite this Lecture
APA style
Cobb, M. (2022, August 30). Human Evolution - The Origin of Humans [Video]. MASSOLIT. https://massolit.io/courses/human-evolution/the-origin-of-humans
MLA style
Cobb, M. "Human Evolution – The Origin of Humans." MASSOLIT, uploaded by MASSOLIT, 30 Aug 2022, https://massolit.io/courses/human-evolution/the-origin-of-humans