The first people to colonize a new area in Quebec had more children and grandchildren than those in existing communities, says a study with widespread implications about human evolution.

In the 17th and 18th centuries, French settlers colonized Quebec. As existing communities grew, waves of immigrants expanded their settlements into new areas.

The first women to settle at the edge of that expansion wave had 15 per cent more children than those in existing settlements, says the study led by Claudia Moreau, a researcher at Sainte-Justine Hospital at the University of Montreal.

The study, based on an examination of birth and marriage records from Quebec church registries between 1686 and 1960, was published Thursday in Science.

The study found that these pioneering settlers' children were also more likely to marry than the children of people who settled in existing communities. In fact, 20 per cent more of the children of the first settlers did marry and had children of their own.

"Given the highly successful history of human colonization, it appears very likely that a considerable fraction of our ancestors have lived on the edge of [the] expansion wave," Damian Labuda, a researcher at the University of Montreal and CHU Sainte-Justine Research Centre who co-authored the study, said at a news conference organized by Science.

He suggested that traits favouring dispersal and reproduction could have evolved specifically during those time periods.

"Could this be the reason for our curiosity of the unknown and our propensity to explore?" he said.

The findings mean the very first settlers in an area have a disproportional effect on the gene pool of subsequent generations and could help explain why some genetic diseases are exceptionally common in the Charlevoix and Saguenay Lac Saint-Jean regions where the study was carried out.

The researchers hypothesize that the main reason the very first settlers had more children was that they had less competition for resources such as land and were therefore able to found a farm, marry and start a family at an earlier age.

Earlier marriage

The records show that on average, women on the wave front married one year earlier than women in established settlements, and went on to have nine children — one more than children in established settlements.

At that time the new areas were settled, there was "absolutely no contraception," said Hélène Vézina, a researcher at the University of Quebec in Chicoutimi who also co-authored the report. Family size was involuntary and limited mainly by the length of women's reproductive lives.

Labuda said that while the researchers don't know the extent to which their results can be generalized to other human expansions, they are eager to do similar studies in other areas with good genealogical records.

The results show "the importance and power of genealogical information to study human evolution," he added.

The researchers noted that studies on the colonization and spread of organisms larger than microorganisms are typically very difficult because each generation extends over a long period of time and it's hard to track them over such periods.

One interesting finding in the study was that certain traits could become more common through natural selection only during times of expansion.

Women who were the earliest settlers in a community and who had an unusually large number of children tended to have children who also had an unusually large number of children.

But there was no such correlation between generations in areas of existing settlements.

Co-author Laurent Excoffier, a researcher at the University of Berne and the Swiss Institute of Bioinformatics in Switzerland, said there has been previous evidence that among other animals, certain characteristics that favour dispersal evolve specifically at a wave front of expansion.

For example, cane toads in Australia tended to grow longer legs during times when they were expanding their range.