Human conditions in southern Africa unraveled by genetic research

Congratulations to the grant! How does it feel?

"I was a bit surprised but really happy because I’ve been thinking about this project for a while. I also applied last year but wasn’t successful. So it was very nice to hear it came through this year. This time my application was much more refined, and I made sure I got a lot of input from people having previously applied as well as from colleagues". 

Born in South Africa, Carina Schlebusch did her PhD at the University of the Witwatersrand. There she focused on the history and movements of African populations, especially the genetic diversity in the Khoisan-speaking populations from southern Africa.  In 2009, she came to Uppsala for post-doctoral studies at the Jakobsson Lab at the Evolutionary Biology Centre.

"There are some very interesting questions about African population genetics, because all of us basically come from Africa. As people moved out of Africa, genetic variation decreased. Therefore, African groups are today the most genetically diversified in the world".

The research questions she hopes to explore in more depth are population movements associated with farming. Her group recently published a paper on the renowned expansion of the Bantu-speaking people from West Africa, who sparkled a major population movement throughout sub-Saharan Africa around 5 000 years ago.

"With an arid and dry desert to the north, they expanded both east- and southwards to areas such as open grasslands suitable for farming".

How is it possible to trace this genetically?
"There are various ways: you can either sequence small parts of the genome, the genetic material of an organism, or you can type markers all across the genome. This is quite easy to do, as humans have these snip chips, basically DNA mutations, containing millions of markers.  After the DNA sample of the population I want to examine has been sequenced here at Uppsala SciLife Lab, I can compare the data with other populations and see how they are related to each other".

A huge collection of samples is assembled at her old university of Witwatersrand, gathered around 30 years ago. But it is only with recent year’s advancements in sequencing technologies that researchers are able to process and analyse genetic material in the millions.

"What I’m basically looking for is human history. The most interesting question we’re trying to address is how human populations moved and interacted with each other in Africa. Various fields have worked on this before, like archaeologists and linguistics, and there are already theories that they have proposed on how people moved. But genetics also have the power to address these questions, and it also adds to the collection of information that people have so far".

This includes tracing the agricultural origins in Africa, which is the focus of her current project. Population movements about 5 000 years ago indicate a rapid spread of farming practices in pockets of South Africa. Some of the Bantu-speaking groups from West Africa eventually attained cattle as well as sheep, and became agro-pastorals. Certain of their genetic markers unravel some interesting details about the development of lactase-persistence. 

"These mutations were selected for as they were beneficial to people keeping animals. Everybody has the ability to process lactose when they’re young, but then the gene gets switched off. But in some populations, the lactose-tolerant gene expression continues until adulthood".

What are the benefits of not tolerating lactose?
"There have been different theories but one of the most commonly accepted one is that it’s not beneficial to the mother if the child continues to drink milk, because then she will only have resources to have one child. She will have to give this child milk for 15-20 years, instead of maybe only six years which would allow her to have several children".   

Carina Schlebusch wants to continue exploring the less known movements by the East-African Khoikhoi population, reaching South Africa prior to the Bantu-speaking people. Will the Khoikhoi, who were herders, also show a lactase-persistent variant? Do they differ genetically from other South African populations?  The answers will fill a void on many levels.   

"When we do our sampling in southern Africa, we’re always going back to the groups we’ve sampled and reporting what we’ve found. The people are very interested and grateful that we’re coming back to them with our reports. Many of these communities were very marginalised and pushed out of society during the colonisation of South Africa. And putting them into focus again through research publications and books makes people aware of the plight of these people".

More information about Carina Schlebusch