The population replacement that occurred with the Neolithic transition in Britain was dramatic. The Western Hunter-Gatherer genetic ancestry that had characterized Britain’s Mesolithic population declined sharply. Brace and colleagues found that by the Neolithic, the British population showed very little hunter-gatherer genetic ancestry — the farming population was genetically dominated by the incoming farmers, with only small amounts of introgression from the earlier hunting population.
This is different from what happened in some other parts of Europe, where the Neolithic transition involved more mixing between farmers and hunter-gatherers, and where hunter-gatherer ancestry resurgences have been documented in some time periods and regions. In Britain, the pattern is one of near-replacement: the Mesolithic hunter-gatherers, including whatever descendants Cheddar Man’s population had, were largely absorbed into or replaced by the Neolithic farming population.
A further demographic upheaval followed during the Bronze Age, around 2500-2000 BCE, when populations associated with the Corded Ware culture and related groups from the Pontic steppe — the grasslands north of the Black Sea — moved into Europe. These populations, sometimes associated with the spread of Proto-Indo-European languages, introduced yet another genetic component into the European population and contributed substantially to the ancestry of modern Europeans. The steppe-related ancestry is today the largest single component of ancestry in many northwestern European populations.
The net result, across these multiple waves of migration and demographic change, is that the modern British population is genetically very different from Cheddar Man’s population. The Western Hunter-Gatherer component of modern British genetics — the contribution from people like Cheddar Man — amounts to a small fraction of the total, mixed through thousands of years of demographic change with the much larger contributions of Neolithic farmers and Bronze Age pastoralists.