19 Dec 2019

Origins - the Big Bang, human evolution & Polynesian migrations

From Our Changing World, 9:06 pm on 19 December 2019

It’s the question parents traditionally dread. ‘Where did I come from?’

How much detail do you go into ... depending on their age, of course ... and what tricky follow-up questions will arise from your answer?

Having faced this question a few times recently from his sons (ages 5 and 8), journalist and science communicator Damian Christie decided to think laterally, and be more prepared the next time the question comes up.


Universe Photo: 123rf

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Exploding stars

University of Auckland astrophysicist Associate Professor J.J. Eldridge.

University of Auckland astrophysicist Associate Professor J.J. Eldridge. Photo: CC-BY-NC-SA 4.0 J.J.Eldridge

For theoretical astrophysist associate professor J.J. Eldridge, from the University of Auckland, the answer to the question “where did I come from?” goes back billions of years and begins with exploding stars.

These are the source of all the elements in our body, from the carbon we’re predominately made up of, to the iron in our blood. In the case of iron, it comes from a particular type of explosion – a white dwarf collapsing and exploding in a binary star system.

“When this thing explodes it can actually outshine all the stars in the galaxy for a few weeks,” says Eldridge. “Which is amazing you’ve got 100-200 billion stars in the galaxy and yet one exploding star can be brighter than all those stars combined.

“And in that, all that carbon and oxygen gets burnt through to iron, and the reaction is so intense and so extreme that you get a sun’s mass worth of iron.”

The earliest humans

Anthropologist Professor Tom Higham from the University of Oxford.

Anthropologist Professor Tom Higham from the University of Oxford. Photo: University of Oxford

We now jump from 4.5 billion years ago, when the earth was formed from the dust of those explosions, to a more recent answer to the ‘where did I come from?’ conundrum.

This answer goes back a mere 200,000 years, and it is the realm of archaeologist and radiocarbon dating specialist Professor Tom Higham, a New Zealander working at the University of Oxford.

Professor Higham’s research includes the exodus of the earliest humans from Africa, and their movements around the world.

We now understand that these movements involved not just killing other human-like species, but interbreeding with them – leaving us with a genetic legacy that can be traced today.

Prof Higham says that at one point, there were probably five or six different human populations that were able to interbreed with one another.

“People like me, who ultimately come from Europe, have around 2.5 percent Neanderthal DNA,” says Higham. “People living in Melanesia, Papua New Guinea, have the same amount of Neanderthal DNA, perhaps a little bit more, but also Denisovan DNA.”

“And so we’re finding that in different parts of the world this genetic legacy - which is a result of our initial movement outside of Africa and our interactions with human groups that were living in Eurasia - has led to what we are today: modern humans.”

This ancient genetic legacy gives us both good and bad outcomes. For the inhabitants of Nepal, for example, it means an ability to breath easier at higher altitudes, while on a less positive note, Neanderthal DNA is thought to be responsible for diabetes.

Professor Lisa Matisoo-Smith, anthropologist at the University of Otago.

Professor Lisa Matisoo-Smith, anthropologist at the University of Otago. Photo: Mark Coote / University of Otago

Polynesian settlement of the Pacific

University of Otago molecular anthropolgist Professor Lisa Matisoo Smith’s work goes back in time a few thousand years and has been hugely influential in our understanding of the pre-European settlement of the South Pacific.

In particular, her work tracing the DNA ancestry of the Polynesian rat, or kiore, has confirmed the path from Aotearoa, back to the mythological home of Hawaiki and even beyond.

“So we can trace the kiore from Aotearoa back to Hawaiki – the Society [Islands] and the Cooks. We can trace those back to West Polynesia. We can trace those kiore back to island South East Asia - but interestingly, they are not native to Taiwan.

“So while the languages which all Polynesians speak and a large percentage of Pacific people speak can be traced back to Taiwan, that’s only the linguistic data,” says Prof Smith.

‘So we can also start to look at the archeological data and the genetic data. So that’s what we’re doing now... looking at human DNA in collaboration with indigenous communities here and across the Pacific.”

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