|
(1) Early human diets | Without Fire? Food processing affected human evolution, even before the invention of cooking. Economist, Mar 12, 2016.
http://www.economist.com/news/sc ... food-make-it-easier
Quote:
"IN 2009 Richard Wrangham, an anthropologist at Harvard, published an intriguing thesis. He was trying to answer a question [why human brains are bigger than other species of Homo genus] * * * Before Dr Wrangham’s work the conventional answer was: 'meat-eating.' Archaeological evidence such as a lack of tool marks on animal bones suggests humanity's ancestors, the Australopithecines, were largely vegetarian. By contrast Homo erectus, the first widespread human being, also ate meat, which is a more compact source of calories than most plant matter
"Dr Wrangham, however, had a different answer: 'cooking.' He showed that the ease of digestion and additional nutritional value made available by treating food with fire (which alters starch and protein molecules in ways that make them easier to digest) boosts its calorific value enough for a reasonable daily intake to power both brain and body—so much so that modern humans who attempt to live only on raw foodstuffs (there are a few who try) have great difficulty remaining well-nourished. On top of this, the softening brought about by cooking could explain a second evolutionary trend, that toward smaller teeth and less-powerful jaws.* * * using tools to chop or pound meat and vegetables [with or without cooking] * * * presumably makes them [food] easier to digest. It also makes them easier to chew, which might account for the reduction in jaw and tooth size.
"The oldest definitive evidence [of Homo erectus cooking food] dates back only 500,000 years, though the species evolved [first appeared] 1.9m years ago. [So, before the invention of cooking, what did Homo erectus do to make food easily chewed?] * * * A paper published in this week's Nature by Katherine Zink and Daniel Lieberman, two of Dr Wrangham's colleagues at Harvard * * * used replicas of the stone tools available to Homo erectus to process food * * * [these two found] that chewing cooked root vegetables required a third less force than was needed to chew an equivalent amount of raw and unprocessed root. Slicing the vegetables did not provide any benefit, but pounding them reduced the force required to chew by about 9%. Pounding meat, by contrast, brought no benefit, whereas slicing it did. As with cooking the vegetables, it reduced the chewing force needed by around a third. Intriguingly, roasting meat [a representative of meat cooking] actually increased the masticatory force required.
My comment:
(a) There is no need to read the rest, so that you can have time to read (2)(b).
(b) Often I wondered (until I read this article) what cooking does to the food. From biochemical point of view:
Cooking starch (rice, noodle, cereal) does not alter 3-dimensional structure or composition 多糖由单糖构成. Heating protein denatures it (meaning the 3-D structure collapses; think scrambled egg), and yet the component remains amino acids 氨基酸. Quotation 2 enlightens me, about contribution of the cooking.
(c)
(i) We humans are Homo sapiens 智人. It is generally understood that Homo erectus is another branch of the evolutionary tree for the Homo genus. See Colin Schultz, Homo Sapiens' Family Tree May Be Less Complicated Than We Thought. Smithsonian Institution, Oct 18, 2013 (blog)
http://www.smithsonianmag.com/sm ... we-thought-2819218/
(family tree)
(ii) "Australopithecines" in quotation 1 is more primitive (and this below) the partial family tree that appears in (c)(i).
Human Family Tree. Smithsonian Institution, undated
http://humanorigins.si.edu/evidence/human-family-tree
One may overlay the cursor to images of humanoid picture to see the names. |
发表于 3-15-2016 06:59:42
收藏
分享
支持
反对
楼主