Charles Darwin published ‘On the Origin of Species’ on 24 November 1859 – 150 years ago. His realisation that evolutionary change could come about naturally – by a combination of passing on of characteristics to the next generation, universal overproduction of offspring, and ‘selection’ of survivors by environmental conditions – shook the world.
Evolution and Genetics
The intricacies of genetics added much to our current understanding of evolution, and the ways in which living things adapt to their environment over time.
Changes occur as populations accumulate new genes or lose old ones. The rate of change is limited by the length of the life-cycles involved.
Rates of Genetic Change
Organisms with a very short life-cycle can respond to environmental changes very quickly. Bacteria, for example, can have life-cycles measured in minutes, and they can respond to changes in months or years.
The emergence of MRSA (methicillin-resistant Staphylococcus aureus) is a perfect example, with methicillin developed in 1959 and the MRSA first discovered in 1961.
Organisms with longer life-cycles (the plants and animals we are most familiar with) adapt much more slowly.
Past Climate Change and Mass Extinctions
- There have been times in the past when the climate altered too rapidly and most species could not cope. The best known of these mass extinctions happened when an asteroid hit the earth about 65 million years ago and the dinosaurs (and many other plants and animals) were wiped out. Looking at these events from a geological perspective reveals that few forms of life can cope with extremely rapid change.
- Some past events that seem to have happened rapidly – such as the start of the most recent ice age around 2.5 million years ago – affected the distribution of plants and animals, but did not lead to mass extinction. ‘Rapidly’ here is to be understood on geological timescales, and, at these rates of change, many plants and animals were able to adapt. Some coped by moving to more favourable conditions (deciduous forest moving south in Europe as the ice took over, then north with the retreat of the glaciers), others by altering their behaviour or modifying their bodies (Woolly Mammoths).
- It is true that the average temperature of the atmosphere has varied widely in the (geological) past, as has the amount of carbon dioxide in the air.
- Plants and animals have successfully adapted to changes much greater than those happening now, or predicted for the near future. They have been able to do this when the rate of environmental change matched the rate of evolutionary change.
- The problem today is not with the increased global temperature predicted, nor with the increased level of carbon dioxide that is anticipated – the problem is with the rate at which the changes are occurring. (See ‘Coral Reef Crisis’ for a concrete example of the way one habitat will change in response to these rapid changes.)
Once the organisms that are unable to cope have become extinct, the survivors will take over and adapt. Life will survive on Earth, but not life as presently known.
Join the Conversation