In the last eight years, the field of ancient DNA research has expanded from just one ancient human genome to more than 1,300. The latest 625 of those genomes debut Feb. 21 in two papers published simultaneously in Nature, including the largest study of ancient DNA to date.

The studies were conducted by international teams each containing more than 100 archaeologists and geneticists and co-led by Harvard Medical School professor David Reich. The results focus on European prehistory in the Stone and Copper Ages.

Findings at a glance:

The Bell Beaker culture comprised at least two genetically distinct populations and initially represented a spread of ideas more than of people, unlike other notable prehistoric archaeological cultures in Europe.

Ninety percent of the population of what is now Britain was completely replaced by an influx of Beaker practitioners around 4,400 years ago, just after the major megaliths at Stonehenge were erected.

The genetic shift introduced variants for paler skin and lighter-colored eyes; genes for digesting lactose became common sometime later.

Multiple pulses of farmers moved from Asia into Europe during the transition from hunting and gathering to agriculture; previously, data was consistent with only a single group giving rise to all European farmers.

Initially, the mixture of incoming Asian farmers and local European hunter-gatherers tended to involve hunter-gatherer women being integrated into farmer communities. Later, the trend reversed and new hunter-gatherer ancestry came mostly from men.

The large sample sizes magnify the power of studies that delve into: