Human Evolution

Where did hominids evolve? Where do we live now?

Out of Africa The fossil record tells us not only when our ancestors lived, but also where In fact it tells us a story about how our ancestors spread out across the Earth

The First Wave All hominids evolved in Africa 1.9 million years ago, Homo erectus was the first hominid species to leave Africa – Spread out over much of Eurasia – Survived until about years ago

The Second Wave A second wave left Africa between and years ago There were the ancestors of the Neanderthals Homo neanderthalensis would eventually populate much of Europe

The New Wave About years ago, modern humans began to migrate out of Africa as well They spread into Europe and Asia, and eventually even into the Americas via a land bridge

Fossils and DNA In some fossils, in rare cases, small traces of organic material can be recovered This is the case with Neanderthals

The Neanderthal Genome We have determined the entire genetic sequence of Neanderthals Small sequences of the Neanderthal genome have been found in modern humans of European and Asian descent Interbreeding likely occurred between Neanderthals and early humans

Cultural Evolution Between and years ago, humans spread over nearly the entire world In this time, human populations around the world developed in entirely different ways In fact, our cultural diversity is one thing that sets us apart from all other species

Cultural Diversity Humans have developed enormously different rituals, customs, and belief systems This is a dramatic behavioural analogy of the founder effect: – in small, isolated populations, new and amazing cultural forms have developed

A Cultural Timeline This cultural evolution has occurred over a relatively brief time period Our ancestors lived as hunter-gatherers for over generations Only in the past 1000 generations has domestication, agriculture, and large population centres developed

Ritual Origins years ago, both humans and Neanderthals were burying their dead and making ornaments It is unknown whether the species developed this trait independently, or if one began copying the other

Language and Communication Our spoken language is an enormous part of our success as a species Language follows its own evolutionary history: – Comparing similarities can help us understand closely related cultures, and helps us understand patterns of migration

The Language Gene? We know that one gene, FoxP2, is essential in speech: even minor defects in it cause severe speech disorders – It is almost identical in all mammals – it is highly conserved – Humans have mutations to the FoxP2 gene

Cultural and Biological Evolution Cultural evolution can influence biological evolution Remember natural selection? – Individuals with the greatest chance of survival are selected for Consider the case of lactose tolerance Lactose tolerance evolved as humans began consuming the milk of domesticated animals – Cows, goats, camels

Lactose Tolerance Lactose is a sugar in milk that was initially hard to digest Those few individuals able to digest lactose were slightly more likely to reproduce (as much as 10% more likely) – Their genes were selected for over time

Cultural and Biological Evolution It was our decision to domesticate these animals and consume their milk that led to this selection event Events like this have happened frequently over the past years

Cultural and Biological Evolution In fact, the rate of evolution for humans has been greater over the past several thousand years than over the previous several million years As we continue to reshape the world, we are also changing our own gene pool

Ongoing Evolution? We synthesize vitamin D using light from the sun Today, we spend less time outside, and use sunscreen to prevent becoming burned This has led to vitamin D deficiency problems in populations What sort of shift in the gene pool might we expect to see as a result?

The Agricultural Revolution For generations, humans numbered in the low millions Agriculture has allowed our population to explode through mass production of food

Our Impact on the Evolution of other Species Domestication has led to changes in the genomes of other species – We know this as artificial selection How much have these domestication events changed the course of human evolution? Today, how hard do we have to work for our next meal?

Textbook Questions Pg. 365 #1, 4, 5, 11