An example: distribution of beetles

The change can also be seen in the distribution of single species. Fossil beetles dating back 38 000 years, when the climate was much cooler, have been found in Britain. They belong to species that are now not found south of northern Scandinavia. Likewise, beetles belonging to species that are now not found north of France have been found in sediments beneath Trafalgar Square in London, from 120 000 years ago when the weather was warmer.

The beetles thus act as indicators of past climates. Another point to note is that the beetles do not show any evolutionary changes in their morphology when the climate changes. As the interglacials and glacials come and go, the beetles do not evolve: they just move north and south.

Figure: two beetle species. Fossil Diachila arctica have been found from 38 000 years ago in Britain and Oodes gracilis from 120 000 years ago.