Updated: Dec 28, 2021
Organisms that have been domesticated by humans are often highly modified compared to their wild ancestors. The application of artificial selective pressure has changed the sizes of specific characters, altered overall body sizes, increased fecundity, and in many cases helped to improve the overall health of stocks. These changes have brought many benefits, most notably lowering consumer costs, and helping to stabilize the global food supply. However, it is becoming increasingly clear that these changes have hidden costs that are not readily apparent.
Theoretical and empirical studies have begun to show that developing organisms have a limited ‘energetic budget’ which they invest in their body parts over the course of juvenile development. Even under optimal nutritional conditions, body parts often compete for limited supplies of circulating macronutrients and growth factors that are needed in increase the sizes of appendages. Ultimately, this means that increases in the size of one body part decreases the amount of material available to construct another, thereby placing a limit on the final size it can attain. Similarly, the maintenance costs of tissues is not free, and as such large, metabolically expensive organs can reduce the amount of energy available for bodily processes such as immune functionality, or general physiological regulation.
This is significant for agriculture because we have often selected for gross increases in the size of specific structures, with little consideration of where the cost of this growth is paid for elsewhere in the body. Many domesticated plants, for example, produce oversized fruits, but this is known to limit the plant’s ability to invest in its own immunity via defensive compounds. Such plants are readily destroyed by insect pests if synthetic pesticides are not applied. Thus, by selecting for something that initially appeared to be entirely beneficial, we have inadvertently become dependent upon the use of external chemicals that are known to negatively impact human health.
Other examples from the animal world can also be found. Egg-laying chickens produce enormous output, both in terms of the size and number of eggs produced. This increase in fecundity has certain benefits, but it is also known to leech the calcium from bones, resulting in feeble birds that can be susceptible to injury. Here too, what initially appeared to be a wholly beneficial selective regime has resulted in consequences that remain poorly understood.
ERI scientists are interested in better understanding the dynamics of competitive and coordinative interactions during juvenile development in order to predict what the true monetary and health costs of centuries of artificial selection are. By studying the dynamics of these processes, we will be in a better position to strengthen the global food supply, reduce our dependence on external pesticides and antibiotics, and create more robust domesticated varieties that will be able to withstand the rigors of human-induced climate change.
Publications by ERI scientists on competition during development: