I suppose humans didn’t always allot 2 to 3 distinct time periods as food-consuming sessions within a day. When and how did that happen? Where did it originate and what does the “epidemiology” look like?
It probably started when hunter-gatherers turned into agriculturists, herders, and farmers. With a population doing more or less similar tasks close to the village (or population center of whatever size or name), it would make sense to assign some people to cook communal meals. These could either be brought out to the workers at a specified time or have the workers come in for a central meal. Far easier and more efficient than one at a time or staggered.
A new study by my very own UC Davis demonstrates that it is an evolutionary method to ensure that the body ingests essential amino acids.
Interesting question.
It is still not clear that humans must eat all 8 essential amino acids together in the same meal (i.e. at the same time), although the citation by CynicalGabe is very thought provoking. Most scientists at the moment seem to agree (in my admitted limited reading) that you will be OK provided you eat all EAA’s within a few hours of each other - so eating some at breakfast and others at lunch (for example) would be OK. Maybe this need / drive to get all EAA’s in a set period of time is fueling some people’s snacking?
I don’t know the answer to your question, but I suspect that **Exapno Mapcase
** is correct. In addition to what he or she said, I would point out that (1) when you switch from grazing on available fruits etc. to some people hunting meat, some people growing or knowing where to find the best veggies/fruits/nuts and some people taking care of domesticated animals (source of eggs, milk, and sometimes meat), then people would naturally want to trade some of what they had/made for some of the other stuff, and would want to prepare a variety of foods to eat at a single sitting (more efficient use of time, less boring meals, and arguably more healthy). Also, because we are social animals, I think that people ate together and found that this time of eating also permitted sharing of information with each other at convenient and predictable times, not to mention companionship and/or socializing.
There is a whole field of nutritional anthropology that looks at this question, among others, as I found when I Googled. This source http://www.unu.edu/unupress/unupbooks/80632e/80632E04.htm was too long for me to go through at this hour of night, but you may find it helpful ( I also suggest you look at section 5 : http://www.unu.edu/unupress/unupbooks/80632e/80632E0i.htm ).