October 30, 2008

Early Food Crops

Early Food Crops
The angiosperms provide most of our food crops. They first appeared in the early Mesozoic or late Paleozoic era about 200 – 250 million years ago, but fossil evidence of them is extremely limited until they began to dominate during the Cretaceous (136 – 190 million years ago). The angiosperms were the first plants to have double fertilization and the enclosure of seeds in fruit. Double fertilization provided zygotes with copious resource to help them get established and fruits attracted animals for dispersal, it was the appearance of the angiosperm that set the stage for the development our mammal ancestors.

A wide range of hypotheses implicating selection have been presented for a rapid emergence and diversification of the angiosperms. The most popular hypothesis is that the concomitant rise of pollinating insects led to powerful divergent selection as foragers and hosts developed complex relationship.

It was the angiosperms that ultimately provided us with most of our crops and their emergence predated the appearance of our species, Homo sapiens. In fact, most of our food families or their close relatives were in existence long before we began farming. The only completely new crop type to appear after the advent of agriculture was maize, Zea mays, which has an ear and tassel arrangement not found in its progenitors. In most cases, human beings did not influence the overall structure of crop species, only the size of their edible organs and their ease of harvest.

Human beings now consume a diverse array of plant structure, and at least 64 families of angiosperms and 180 genera are utilized as crops. This is a broad systematic group, but represents only a small fraction of the total number of angiosperm families (300) and genera (3000). The dicotyledons provide the highest number of crop plants; however, the bulk of the world is fed by a few monocotyledonous grains (maize, rice and wheat).
Early Food Crops

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