SCIENCE

Australia was one of the first regions modern humans reached after leaving Africa some 50,000 years ago. And no one visited them for a long time. (Christian Science Monitor)

Use our resources to trace our “global human journey” out of Africa.

Scroll down for a quick list of key resources in our Teachers’ Toolkit.

Discussion Ideas

• The new paper discusses genetic research on the Y chromosome, which is part of the human genome. What is the difference between genes, chromosomes, and genomes? Take a look at this great guide for some help.
  • Genes, chromosomes, and genomes are defined by DNA, a molecule that contains our unique genetic code. DNA exists in “base pairs” of nucleotides: adenine, cytosine, guanine and thymine.
    • chromosome: Long single strands of DNA are coiled up into structures called chromosomes. Human beings have 23 pairs of chromosomes.
      • The Y chromosome is one of two sex chromosomes in humans. (The other is the X chromosome.) The Y chromosome is usually only present in males, who have an XY pair, while most females have an XX pair.
    • gene: Sections of DNA on our chromosomes are “read” together as genes. Genes contain the instructions for our individual characteristics, like eye and hair color.
    • genome: A genome is an organism’s entire set of genes and chromosomes. A genome holds all the inherited characteristics of an organism—what makes a banana a banana, or a human a human. The human genome is approximately 3 billion base pairs long, packed in our 46 chromosomes.

• The Christian Science Monitor discusses migration to Sahul through the Wallace Line. What? I thought we were talking about Australia.
  • We are. Sahul is the name of the ancient continent that encompasses present-day Australia, Papua New Guinea, and Tasmania. Although Sahul is an ancient landmass, it still emerges from the briny deep depending on the surrounding sea level. The last time Sahul emerged as a whole from the Indian and Pacific Oceans was during the last ice age, about 18,000 years ago.
  • The Wallace Line is one of three major (and majorly contested) biogeographical lines in Southeast Asia. Biogeography describes the distribution of species and ecosystems in space and time. The Wallace Line separates the ecozones of Australia and Wallacea. (Wallacea is a transition zone between Australia and Southeast Asia, sometimes called Indomalaya.) The Wallace Line was largely uncrossed for thousands of years—which is why Australian fauna is so amazingly distinct from fauna from anywhere else.

• Geneticists have known humans reached what are now Australia and Papua New Guinea about 50,000 years ago. This is not news. So what is surprising about the new genetic research?
  • That no one joined them. According to the Christian Science Monitor, “Some scientists have said the archaeological record hints at an influx of new people around 4,000 to 5,000 years ago from India. At that time, languages and stone tools changed significantly, and Australian wild dogs, dingoes, arrived. But geneticists found no evidence of such a migration in the Y chromosome of indigenous people living there today.” This is fascinating.

• So, “If the new stone tools and new languages cannot be explained by the immigration of a distinct population, what actually happened” 5,000 years ago to create the new, changed culture?
  • Great question! The CSM offers three possible ideas:
    • A changing climate or available resources could have precipitated the need for new technology or ways of communicating.
    • Previous studies have suggested a link between environmental changes and language.
    • Perhaps the population reached a critical mass and prompted the people to begin innovating.
  • And the dingoes? They could have been brought back from an expedition to South Asia by some of the people already living on Sahul, or visitors to Sahul could have left the dogs, but not their DNA.

TEACHERS’ TOOLKIT

Christian Science Monitor: Australian Aborigines spent 50,000 years isolated from the rest of us

Nat Geo: Global Human Journey video

YourGenome: What is a genome?

(extra credit!) Current Biology: Deep Roots for Aboriginal Australian Y Chromosomes