Dr David Walker will confuse people by stating "vegetarianism is a step in man's evolution" (Letters, May 17). Yet he confuses social change with evolutionary change. In order for humans to "evolve" into vegetarians, there would have to be a gene, or genes, to confer a genetic advantage to those humans who eat only vegetables so that their genes would spread through the population in preference to those of omnivores.

Merely because my parents ate only vegetables would not mean that I would be born wanting to eat only vegetables. I may choose that diet, but not because of genetic pressure. I have no problem with vegetarians but humans will continue to want to eat meat until the stars go out (unless Dr Walker knows something I don't).

John Mulraney, 111 Watson Street, Motherwell.

It was disappointing to see Dr Andrew Kelly missing a key issue regarding the evolution of human beings and vegetarianism (Letters, May 18). This is that we have the luxury to choose whether or not we wish to kill other animals in order to consume their flesh.

It is inaccurate to claim that becoming a vegetarian will not improve animal welfare. Yes, buying meat and other animal products from animals reared in farming systems such as free range and organic that offer higher welfare than intensive systems will help to reduce suffering. However, choosing to eat a vegetarian or vegan diet removes the need for any animals to be bred, farmed and slaughtered in the first place.

Dr Kelly is right that we should press governments to improve the welfare of farmed animals. However, reducing or eliminating the consumption of meat and animal products is a humane, healthy, and environmentally-friendly option.

Ross Minett, Director, Advocates for Animals, 10 Queensferry Street, Edinburgh

I have just read the letter from Dr David Walker. Prior to reading it I had not realised I was cerebrally challenged and completely thoughtless. It had not occurred to me that wanting to have fish with my chips or mince with my carrots and tatties meant I was intellectually inferior to those who have vegetarian views.

I have some vegetarian friends and respect their views, just as I would expect them to respect mine. I am very unobservant, however, and had not realised how much more intelligent they are. I also am a keen vegetable grower in my garden and we regularly enjoy leeks, onions, lettuce, parsnips, broccoli, spring onions, parsley and other herbs straight from the vegetable plot. I would never dream, though, of seeking to force my views (or diet) on those of a contrary position, unlike Dr Walker.

P Houston, 1Westfield Drive , Kilmacolm.