Friday, February 22, 2013

Evolution on Cattle

Whenever you see a hamburger or a glass of milk do you sometimes  stop to think about how they came about?  We know that these came from cows but what was the process pertaining to it and how did evolution shift for the cows of our time?

Cattle have been domesticated since the early Neolithic.  The entire species may have originated from 80 aurochs tamed in Mesopotamia 10,500 years ago in Turkey and Iraq (Wilkins).  Cows are very efficient in that they are very easy to breed because they can survive on such few things like water and grass and still produce copious amounts of milk and efficiently build muscles.  Their anatomy – especially the usage of  the rumen, and the efficiency of selective breeding, are partly the reason why genetically modified cattle are so popular today.    

Early cattle served a triple-purpose. They provided meat, milk and labor to their owners. Eventually their purposes were changed and they were selected more for single or in some cases dual purposes. Today, cows are genetically modified to produce more muscles. These cows generally have shorter legs and a stumpier look.  Humans have exaggerated genetics to get desired traits and there are currently over 800 different modified cattle.  The dairy cattle qualities are focused on the size of the udders and the skin, while the cattle used for meat focuses on the sheer size of the animal. The English longhorn is an example of a cow that is bred purely for beef.  In America, the most popular meat that we use is from the Aberdeen Angus. 

Scientists continue to  selectively  breed cattle to fit human needs.  Research has shown that some genetically modified cows can produce milk that is hypoallergenic.  This would be beneficial to individuals who are lactose intolerant, especially infants.  However, this alters the cattle genome and isn’t beneficial to the cattle.  For example, over the last hundred years milk yield in dairy cattle increased from 2000kg to nearly 8000kg per annum (Gamborg).  Some disadvantages for the cattle are that this excessive breeding for high milk yields creates animal health problems like digestive disorders and reduced fertility (Gamborg).  Another disadvantage is the lack of variety among selective breeding. The differences in genome for ancient cows verses the genome now is extremely minute whereas if it wasn’t for the domestication there would have been more variety. (Wilkins).

I do sympathize with the animals.  Due to human involvement in cattle, they have not evolved naturally in the way that most organisms have.  Yes, they are beneficial to us but at what cost?  Some notable costs are the loss of variety among cattle and the struggle for these animals to become fully adapted to a natural environment without human interference.

word count: 455 words

Works Cited

Gamborg, C. and Sandoe, P.  “Breeding and biotechnology in farm animals-ethical issues” RoutledgeFalmer.


Wilkins, Alasdair. “DNA reveals that cows were almost impossible to domesticate” 28 March 2012.


  1. You mention that dairy cows bred for higher milk yields often experience health problems such as digestive disorders. Do other types of genetically-modified cows, such as ones bred for meat, also have health problems or decreased fertility? Ethically it seems like genetically breeding cows (and other animals and plants) is wrong but in order to feed the world it is becoming necessary. Are there certain restrictions, laws, regulations that protect the integrity of the animals?

  2. The manipulation of animals to yield benefits for humans at the expense of their health and genetic variation brings up a tremendous amount of ethical questions. A major question that comes to mind is has there been any research on selecting for greater milk production traits while minimizing the negative impact on health? What is the relationship between the genes controlling milk production and the genes regulating proper digestion? Why is it that selecting the desired milk production traits causes deleterious alleles that encourage health issues to be expressed as well?

  3. Your post reminded me of a book I read a few months ago. The author asserted that as dairy production became more industrialized, certain species of cows were selected for better milk production. This over time has led to a decreased number of domesticated cattle species. While this fact combined with the other negative ramifications you mention are unfortunate, I wonder if anything can actually be done to reverse the trend? Is it even possible to reintroduce cattle to the wild? It seems as though we've bred cattle to the point where they would not be able to survive well against predators.

  4. It is interesting to compare artificial selection today with the methods used in the past. Both select preferred organismal traits, but where is the ethical line between acceptable and too much? It puts in question the role of human intervention in the natural evolutionary process.

  5. It is slightly depressing to contemplate the pervasive effects that humans have on other animals, often at the latter’s expense. Being from a family that owns cattle, I appreciated your succinct wording in illustrating the effects of cattle domestication. Considering that we know some detrimental effects associated with selective cattle breeding, but continue with the process, is concerning because it shows that humanity’s sense of entitlement can harm both animals and ourselves.

  6. The difference in the genetic diversity sounds like these cows are heavily inbred. Inbred animals are usually more susceptible to virus and disease-causing agents, but this is be made up by injecting antibiotics and vaccines to these cows. This is the same with other domestication examples (pets and vets).