OHS2020 Chap6

What caracterises Homo Sapiens ?

Homo sapiens are characterized by many different aspects distinct from the other Homo species. We recognize specific features in every living humans that allow us to qualify them as the only human species on our Earth. These specific features consist on "the skeleton braincase, a small face tucked under the forehead, a chin under the lower jaw, small and separated brow ridges, narrow shoulders, trunk and pelvis". The Humans are also known for needing a long ans slow gain in maturity which is a typical specific modern human feature.--NoraM (discussion) 20 avril 2020 à 14:30 (CEST) Our middle and inner ear anatomies and our microscopic dental structure are also different from other human species.

Where were living the different human species ?

We found fossils, DNA and bowns of different human species in many different regions. It allowed us to determine that H. sapiens was living in Africa, Europe, Asia and Oceania. H. neanderthalensis territories were in Eurasia. We also know that another spicies, Denisovans were living near Denisova cave and in Sunda. --ColetteB (discussion) 30 avril 2020 à 17:12 (CEST)

What caracterized the Early Homo sapiens ?

Early Homo spiens had a larger brain volume and a larger brow ridge than modern humans, but he had a chin and a flat face like a modern humans. The shape of his skull was more diverse, varying between archaic and modern traits.(p.136) —JeremyS

it might be interesting to compare Early and Modern Homos.--Pierre.brawand (discussion) 7 mai 2020 à 15:58 (CEST)

How does the image on p.143 challenge the definition we have today of a "species"?

A species is a group of individuals that, if they mate, have the potential to generate fertile offspring. However, what is problematic of the image on p.143 is the existence of interbreeding between different species that gave rise to fertile descendants, which led to the existence of modern humans, us. So, how come this happened? A hypothesis is that even though we are talking about different species, they are closely related enough (cousins) to have been able to reproduce. We now know that humans carry around 2% of Neanderthal DNA in our genomes, due to these interbreeding events, and some others have a higher percentage of DNA coming from ancestors who used to live in the same region, like for example Oceanians having more derived DNA from Denisovans. The reason we may still show signs of these past species is because the interbreeding passed on favorable traits from different species that could have been helpful for our survival. --GavinC (discussion) 5 mai 2020 à 10:38 (CEST)

it might be interesting to define how much "foreign" DNA we have today in our genome? This might explain that despite the sexual reproduction we use with meiotic and recombination mechanisms, the Neanderthal DNA persists in our DNA.-Pierre.brawand (discussion) 5 mai 2020 à 10:52 (CEST)

What is the biological species concept (BSC)?

The biological species concept is one of the several ways to define a species. This concept defines a species as a population (Members of the same species ) of organisms that can interbreed together to produce viable, fertile offspring and cannot produce viable offspring with members of other species. --ChloeS (discussion) 6 mai 2020 à 17:45 (CEST)

Why does interbreeding challenge the BSC?

The 'biological species concept' argues that inviduals that could reproduce with one another resulting in fertile offsprings are of the same species. But this would mean that H. neanderthalensis, H. denisovensis and H. sapiens were one species, as interbreeding happened between them according to DNA analysis. Yet we can still identify different lineages in fossils, based on their morphological traits, so the frequency of the interbreeding ought to be low enough not to make them a single species.

The same problem exists in living species, where interbreedings can happen between two species but the species are recognized as distinct, for instance grizzly bears and polar bears. (p.151)—JeremyS

Why is Homo sapiens the only remaining species out of the ones discussed in this book (p.149)?

There are many factors that potentially explain the survival of our species, including a higher diversity and larger numbers compared to other species, the fact that we may have occupied the most favorable environments at the expense of the other species, and more effective hunting and gathering methods. --GavinC (discussion) 6 mai 2020 à 15:17 (CEST)

Which species gave rise to the first true humans?

While species like Sahelanthropus, Orrorin and Ardipithecus all displayed hominin characteristics (bipedalism, small canines...), they also showed many ape-like signs, thus not providing enough convincing proof to validate this hypothesis. However, Australopithecus may be the closest species we have to an answer, but let's not forget that any conclusions we form based on findings are still quite uncertain and we will just have to wait in the future for this question to be more clear. --GavinC (discussion) 6 mai 2020 à 15:46 (CEST)

What's the Computerized Tomography ?

It's is an X-Ray technique that combines a series of X-ray images taken from different angles around the body and uses computer processing to create cross-sectional images (it creates images in 3D) of the bones, blood vessels and soft tissues inside your body. The CT scan creates images (virtual "slices") of specific areas of a scanned object, allowing the user to see inside the object without cutting.--GaetanP (discussion) 7 mai 2020 à 15:42 (CEST)

Why are we considered as "the last survivors of a compley evolutionary radiation"(p.151) ?

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Because our closest relatives such as Neanderthals or Denisovans all went physically extinct whilts modern humans grew in number. The global spread of modern humans induced the lose of physical traits of their closest relatives. --ChloeS (discussion) 7 mai 2020 à 16:21 (CEST)