Dalmatian overlooking the Ecuadorian plains

Directed evolution

For thousands of years humans have tried to harness the best of nature by modifying crops, animals and even decorative plants or flowers

The domestication of crops was one of the most important events in human history. For generation after generation, our ancestors selected seeds from plants with favourable features to obtain crops that could provide a steady food supply.

In 2006, Israeli scientists suggested that figs were the first crop to be domesticated, around 11,000 years ago. The most significant crops, however, are the cereals – rice, wheat, maize and sorghum.

Modern cereals are the result of generations of selection for plants with beneficial properties. Sometimes, the original plant still exists; maize, for example, is derived from the tropical grass teosinte. Genetic comparisons can thus be made to identify the genetic basis for cereals’ useful properties – which is easier now that the genomes of many crop species have been sequenced.

Cereal crops, for example, were eventually developed with grains that stay attached to stalks until they are harvested, rather than grains that fall (‘shatter’). Fine-tuning two genes that were recently discovered to control shattering might now help modern farmers produce even better future crops.

Interestingly, the same ‘shattering’ gene is altered in domesticated sorghum, rice and maize, but in different ways. The artificial selective pressures of domestication have independently led to the same genetic end result in the three crops.

Spotted history

Dogs are domesticated wolves. The domestication of dogs occurred between 9,000 and 34,000 years ago, before humans’ widespread use of agriculture. Genetic comparisons between dogs and wolves have shown that the two are distinct, with no present-day wolf lineage likely to be the source of today’s domesticated animals. Today’s dogs may all be descended from a now-extinct wolf lineage.

Pedigree dogs have been selectively bred to emphasise particular characteristics. Inbreeding reduces the gene pool, and many breeds of dog are prone to genetic conditions affecting their health. Dalmatians, for example, are often deaf.

Lead image:

Geee Kay/Flickr CC BY NC ND

References

Questions for discussion

  • Do you think selective breeding of dogs should be allowed?

About this resource

This resource was first published in ‘Evolution’ in January 2007 and reviewed and updated in December 2014.

Topics:
Ecology and environment, Genetics and genomics, History
Issue:
Evolution
Education levels:
16–19, Continuing professional development