The greatest threat to the world's crops, however, is not a major volcanic eruption or an asteroid strike; rather, it is the routine practices of commercial agriculture. Today, most crops are grown from a tiny number of patented seed varieties, which have been designed not only for maximum yield, but also for such features as resistance to common herbicides and a long supermarket shelf life. As a result, large quantities of food can be produced much more efficiently than in the past, but many crop varieties and animal breeds that are not as well suited to mass production have become extinct or are on the verge of extinction.
The sustainable farming movement seeks to preserve biodiversity by planting heirloom seeds and raising heritage livestock breeds on small farms. Sustainable farmers point out that these seeds and animals are particularly well adapted to local environmental conditions and that some of their genetic traits may turn out to be valuable on a larger scale as the planet adapts to climate change. In addition, history has shown that a lack of biodiversity in agriculture is dangerous; if a widely planted crop variety is ruined by blight or pests, or if a livestock disease spreads quickly through genetically identical animals, people can end up starving in large numbers. The Irish potato famine in the 1840s happened because the potatoes in Ireland were all of the same variety and were all destroyed by the same blight.
There are many individuals and organizations working to protect endangered seed varieties and livestock breeds from extinction. They understand that biodiversity has a value in itself, even if a particular seed variety may not result in the highest yield or produce crops of a consistent shape or color.
Many of the same considerations hold true when it comes to preserving the diversity of the human genome. For our species to have the best chance to survive and flourish, we must be able to adapt in many ways to the unforeseen changes that await us. Moreover, the modern economy is becoming increasingly specialized, and employers need to find workers with different cognitive traits and social behaviors to fill the many different niches in their companies. A workforce made up of near-identical employees with a narrow set of abilities would be grossly inefficient.
Imagine a society where many educators and medical professionals adhered to the same philosophy as the sustainable farmers. Parents might be told that their young autistic child was like a rare flower or bird, ideally suited to certain kinds of environments. Genetic diversity in the human species would be treasured.
Maybe we'll get there someday. Until then, for a discussion of the sort of attitude we have to contend with at present, I recommend Bev's recent article about being removed from the general catalog of humanity.