Prehistoric humans rarely mated with their cousins
Scientists screened 1,785 ancient humans genomes from the last 45,000
years for parental relatedness

Date:
September 14, 2021
Source:
Max Planck Institute for Evolutionary Anthropology
Summary:
At present-day, more than ten percent of all global marriages
occur among first or second cousins. While cousin-marriages are
common practice in some societies, unions between close relatives
are discouraged in others.

In a new study, researchers investigated how common close parental
relatedness was in our ancestors.



FULL STORY ==========================================================================
The researchers re-analyzed previously published DNA data from ancient
humans that lived during the last 45,000 years to find out how closely
related their parents were. The results surprising: Ancient humans
rarely chose their cousins as mates. In a global dataset of 1,785
individuals only 54, that is, about three percent, show the typical
signs of their parents being cousins. Those 54 did not cluster in space
or time, showing that cousin matings were sporadic events in the studied ancient populations. Notably, even for hunter-gatherers who lived more
than 10,000 years ago, unions between cousins were the exception.


==========================================================================
To analyze such a large dataset, the researchers developed a new
computational tool to screen ancient DNA for parental relatedness. It
detects long stretches of DNA that are identical in the two DNA copies,
one inherited from the mother and one from the father. The closer
the parents are related, the longer and more abundant such identical
segments are. For modern DNA data, computational methods can identify
these stretches with ease. However, the quality of DNA from bones that
are thousands of years old is, in most cases, too low to apply these
methods. Thus, the new method fills the gaps in the ancient genomes
by leveraging modern high-quality DNA data. "By applying this new
technique we could screen more than ten times as many ancient genomes
than previously possible," says Harald Ringbauer from MPI-EVA, the lead researcher of the study.

Beyond identifying matings of close kin, the new method also allowed
the researchers to study background relatedness. Such relatedness
originates from the typically many unknown distant relationships within
small populations. As a key result, the researchers found a substantial demographic impact of the technological innovation of agriculture. This
was always followed by a marked decay in background parental relatedness, indicative of increasing population sizes. By analyzing time transects of
more than a dozen geographic regions across the globe, the researchers
expanded upon previous evidence that population sizes increased in
societies practicing farming compared to hunter- gatherer subsistence strategies.

The new method to screen ancient DNA for parental relatedness gives
researchers a versatile new tool. Looking forward, the field of ancient
DNA is quickly developing, with more and more ancient genomes being
produced every year. By elucidating mating choices as well as the dynamics
of past population sizes, the new method will allow researchers to shed
more light on the lives of our ancestors.

========================================================================== Story Source: Materials provided by Max_Planck_Institute_for_Evolutionary_Anthropology. Note: Content may
be edited for style and length.


========================================================================== Journal Reference:
1. Harald Ringbauer, John Novembre, Matthias Steinru"cken. Parental
relatedness through time revealed by runs of homozygosity in
ancient DNA.

Nature Communications, 2021; 12 (1) DOI: 10.1038/s41467-021-25289-w ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/09/210914124950.htm

--- up 1 week, 5 days, 8 hours, 25 minutes
* Origin: -=> Castle Rock BBS <=- Now Husky HPT Powered! (1:317/3)