Because we didn't need to. We have bigger brains and began making tools.
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Is dietary orientation and/or classification; e.g. vegetarian and omnivore, a nature or a choice?
- Thread starter Smart_Guy
- Start date
Because we didn't need to. We have bigger brains and began making tools.
What nonsense. As I remember, the proposition that "meat-eating was a crucial element of human evolution" was not what that study found (or was able to conclude).
The Importance of Dietary Carbohydrate in Human Evolution
Abstract
We propose that plant foods containing high quantities of starch were essential for the evolution of the human phenotype during the Pleistocene. Although previous studies have highlighted a stone tool-mediated shift from primarily plant-based to primarily meat-based diets as critical in the development of the brain and other human traits, we argue that digestible carbohydrates were also necessary to accommodate the increased metabolic demands of a growing brain. Furthermore, we acknowledge the adaptive role cooking played in improving the digestibility and palatability of key carbohydrates. We provide evidence that cooked starch, a source of preformed glucose, greatly increased energy availability to human tissues with high glucose demands, such as the brain, red blood cells, and the developing fetus. We also highlight the auxiliary role copy number variation in the salivary amylase genes may have played in increasing the importance of starch in human evolution following the origins of cooking. Salivary amylases are largely ineffective on raw crystalline starch, but cooking substantially increases both their energy-yielding potential and glycemia. Although uncertainties remain regarding the antiquity of cooking and the origins of salivary amylase gene copy number variation, the hypothesis we present makes a testable prediction that these events are correlated.
We propose that plant foods containing high quantities of starch were essential for the evolution of the human phenotype during the Pleistocene. Although previous studies have highlighted a stone tool-mediated shift from primarily plant-based to primarily meat-based diets as critical in the development of the brain and other human traits, we argue that digestible carbohydrates were also necessary to accommodate the increased metabolic demands of a growing brain. Furthermore, we acknowledge the adaptive role cooking played in improving the digestibility and palatability of key carbohydrates. We provide evidence that cooked starch, a source of preformed glucose, greatly increased energy availability to human tissues with high glucose demands, such as the brain, red blood cells, and the developing fetus. We also highlight the auxiliary role copy number variation in the salivary amylase genes may have played in increasing the importance of starch in human evolution following the origins of cooking. Salivary amylases are largely ineffective on raw crystalline starch, but cooking substantially increases both their energy-yielding potential and glycemia. Although uncertainties remain regarding the antiquity of cooking and the origins of salivary amylase gene copy number variation, the hypothesis we present makes a testable prediction that these events are correlated.
The Importance of Dietary Carbohydrate in Human Evolution on JSTOR
The authors go on to note:
Although the timing of widespread cooking is not known, Wrangham and Conklin- Brittain (2003) argue that it was long enough ago to allow for biological adaptations to take place, including changes in digestive anatomy around 1.8 million years ago, reduction in tooth size, and reduced capacity for digestion of raw, fibrous foods. They further propose that cooked foods were soft enough to be palatable by infants, potentially leading to earlier weaning and shorter interbirth intervals (also see Carmody et al. 2011).
Ancestral Diet
Plants produce a wide range of carbohydrates to serve as energy reserves or for structural functions. Reserve carbohydrates can be deposited in underground storage organs (USOs) such as roots, tubers, and rhizomes, or above ground in seeds, certain fruits and nuts, and in the inner bark of some trees. Starch constitutes up to 80% of the dry weight of edible roots and tubers and, if left undisturbed in the ground, they remain stable and can be harvested as needed over a period of months. USOs can also be dried to increase durability and portability, and have been proposed as important foods for early hominins (Laden and Wrangham 2005). The ability to exploit starch-rich roots and tubers in early hominin diets is considered a potentially crucial step in differentiating early Australopithecines from other hominids and to have permitted expansion into new habitats (Wrangham et al. 1999; Laden and Wrangham 2005). The consumption of USOs could also explain differences in dentition between early hominins and African apes (Laden and Wrangham 2005). USO-rich aquatic habitats such as deltas have been proposed as an intermediate niche in the adaptation of early hominins to savanna habitats, with the need to forage in shallow water promoting bipedality (Wrangham 2005, 2009). O’Connell et al. (1999, 2002) suggest that postmenopausal females played a central role in foraging for USOs and food sharing, which directly enabled younger female relatives to reproduce more frequently. They further proposed that meat formed an irregular component of the diet and that hunting by early hominins may have been as much to do with status as nutrition, something that has also been proposed for chimpanzees (Nishida et al. 1992; Stanford 1998). Although meat may have been a preferred food, the energy expenditure required to obtain it may have been far greater than that used for collecting tubers from a reliable source (Carmody et al. 2011).
Many other lines of evidence support consumption of starchy USOs by early hominins. Correlation of evidence for C4 plants in the diet of Australopithecus africanus and Paranthropus robustus, and specific-use wear traces on teeth are proposed to be indicative of consumption of sedge corms (Dominy et al. 2008; Ungar and Sponheimer 2011; Grine et al. 2012; Ungar et al. 2012). A C4 signal identified in the tooth enamel of a 3-million-year-old Australopithecus bahrelghazali from Chad has been interpreted as evidence for exploitation of Cyperaceae sedge tubers (Lee-Thorp et al. 2012). Evidence of abundant suids in many African hominin sites has been taken to suggest that USOs, the predominant food source for these animals, were plentiful (Reed and Rector 2007). The presence of palms in the Olduvai Gorge region date from around 1.8 mya (Albert et al. 2009); palms often have abundant edible starch in their trunks, and some species also produce dates. The roots of lilies (Liliaceae), rushes (Juncaceae), and sedges (Cyperaceae) have also been identified at Olduvai Gorge from a horizon dated to between 1.89 and 1.75 million years ago (Bamford et al. 2008). Edible USOs from these monocotyledons, along with grasses (Poaceae) identified at the same sites, offer evidence for the abundance of edible starch at a time that hominins were present.
Ancestral Diet
Plants produce a wide range of carbohydrates to serve as energy reserves or for structural functions. Reserve carbohydrates can be deposited in underground storage organs (USOs) such as roots, tubers, and rhizomes, or above ground in seeds, certain fruits and nuts, and in the inner bark of some trees. Starch constitutes up to 80% of the dry weight of edible roots and tubers and, if left undisturbed in the ground, they remain stable and can be harvested as needed over a period of months. USOs can also be dried to increase durability and portability, and have been proposed as important foods for early hominins (Laden and Wrangham 2005). The ability to exploit starch-rich roots and tubers in early hominin diets is considered a potentially crucial step in differentiating early Australopithecines from other hominids and to have permitted expansion into new habitats (Wrangham et al. 1999; Laden and Wrangham 2005). The consumption of USOs could also explain differences in dentition between early hominins and African apes (Laden and Wrangham 2005). USO-rich aquatic habitats such as deltas have been proposed as an intermediate niche in the adaptation of early hominins to savanna habitats, with the need to forage in shallow water promoting bipedality (Wrangham 2005, 2009). O’Connell et al. (1999, 2002) suggest that postmenopausal females played a central role in foraging for USOs and food sharing, which directly enabled younger female relatives to reproduce more frequently. They further proposed that meat formed an irregular component of the diet and that hunting by early hominins may have been as much to do with status as nutrition, something that has also been proposed for chimpanzees (Nishida et al. 1992; Stanford 1998). Although meat may have been a preferred food, the energy expenditure required to obtain it may have been far greater than that used for collecting tubers from a reliable source (Carmody et al. 2011).
Many other lines of evidence support consumption of starchy USOs by early hominins. Correlation of evidence for C4 plants in the diet of Australopithecus africanus and Paranthropus robustus, and specific-use wear traces on teeth are proposed to be indicative of consumption of sedge corms (Dominy et al. 2008; Ungar and Sponheimer 2011; Grine et al. 2012; Ungar et al. 2012). A C4 signal identified in the tooth enamel of a 3-million-year-old Australopithecus bahrelghazali from Chad has been interpreted as evidence for exploitation of Cyperaceae sedge tubers (Lee-Thorp et al. 2012). Evidence of abundant suids in many African hominin sites has been taken to suggest that USOs, the predominant food source for these animals, were plentiful (Reed and Rector 2007). The presence of palms in the Olduvai Gorge region date from around 1.8 mya (Albert et al. 2009); palms often have abundant edible starch in their trunks, and some species also produce dates. The roots of lilies (Liliaceae), rushes (Juncaceae), and sedges (Cyperaceae) have also been identified at Olduvai Gorge from a horizon dated to between 1.89 and 1.75 million years ago (Bamford et al. 2008). Edible USOs from these monocotyledons, along with grasses (Poaceae) identified at the same sites, offer evidence for the abundance of edible starch at a time that hominins were present.
The Importance of Dietary Carbohydrate in Human Evolution on JSTOR
Hardy et al. cite the important recent work of Suzana Herculano-Houzel on primate brain scaling and number of neurons. In a series of studies, she and Karina Fonseca-Azevedo show brain growth among Homo erectus could only have been achieved by way of the increased calories and glucose obtained from a cooked diet:
Metabolic constraint imposes tradeoff between body size and number of brain neurons in human evolution
Metabolic constraint imposes tradeoff between body size and number of brain neurons in human evolution
It only makes sense that the “major driving force to the rapid increase in brain size in human evolution” was the shift to a cooked diet, not meat-eating as speculated by some--if meat-eating were the factor that leads to brain development, then it would be carnivores, not humans, with the neuron-rich brains. Humans are not biologically adapted to meet their daily energy requirements by eating other animals; carnivores are. See Milton and Zucoloto below. Humans are not biologically adapted to catch and kill other animals of any significant size without great expenditures of energy. What distinguishes early Homo from all other animals is not eating meat but cooking food.
The following is from Herculano-Houzel’s 2012 study published in June prior to the November 2012 publication:
The remarkable, yet not extraordinary, human brain as a scaled-up primate brain and its associated cost
In a letter published in American Journal of Clinical Nutrition in 2000, Katharine Milton pointed out:
Reply to L Cordain et al
Zucoloto’s 2011 review in Psychology and Neuroscience provides further details:
Evolution of the human feeding behavior
http://psycnet.apa.org/journals/pne/4/1/131.html
In Milton’s 1999 paper, after noting the variety of ways that humans are biologically distinguished from carnivores, she discusses some of the known detrimental effects of high-protein diets on non-carnivores. Ultimately she points out that “adult humans apparently cannot catabolize sufficient protein to meet more than 50% of the daily energetic requirements.”
Metabolic constraint imposes tradeoff between body size and number of brain neurons in human evolution
Abstract
Despite a general trend for larger mammals to have larger brains, humans are the primates with the largest brain and number of neurons, but not the largest body mass. Why are great apes, the largest primates, not also those endowed with the largest brains? Recently, we showed that the energetic cost of the brain is a linear function of its numbers of neurons. Here we show that metabolic limitations that result from the number of hours available for feeding and the low caloric yield of raw foods impose a tradeoff between body size and number of brain neurons, which explains the small brain size of great apes compared with their large body size. This limitation was probably overcome in Homo erectus with the shift to a cooked diet. Absent the requirement to spend most available hours of the day feeding, the combination of newly freed time and a large number of brain neurons affordable on a cooked diet may thus have been a major positive driving force to the rapid increased in brain size in human evolution.
Despite a general trend for larger mammals to have larger brains, humans are the primates with the largest brain and number of neurons, but not the largest body mass. Why are great apes, the largest primates, not also those endowed with the largest brains? Recently, we showed that the energetic cost of the brain is a linear function of its numbers of neurons. Here we show that metabolic limitations that result from the number of hours available for feeding and the low caloric yield of raw foods impose a tradeoff between body size and number of brain neurons, which explains the small brain size of great apes compared with their large body size. This limitation was probably overcome in Homo erectus with the shift to a cooked diet. Absent the requirement to spend most available hours of the day feeding, the combination of newly freed time and a large number of brain neurons affordable on a cooked diet may thus have been a major positive driving force to the rapid increased in brain size in human evolution.
Metabolic constraint imposes tradeoff between body size and number of brain neurons in human evolution
It only makes sense that the “major driving force to the rapid increase in brain size in human evolution” was the shift to a cooked diet, not meat-eating as speculated by some--if meat-eating were the factor that leads to brain development, then it would be carnivores, not humans, with the neuron-rich brains. Humans are not biologically adapted to meet their daily energy requirements by eating other animals; carnivores are. See Milton and Zucoloto below. Humans are not biologically adapted to catch and kill other animals of any significant size without great expenditures of energy. What distinguishes early Homo from all other animals is not eating meat but cooking food.
The following is from Herculano-Houzel’s 2012 study published in June prior to the November 2012 publication:
It can thus be seen how any increase in total numbers of neurons in the evolution of hominins and great apes would have taxed survival in a limiting, if not prohibitive, way, given that it probably would have to occur in a context of already limiting feeding hours: The added 60 billion brain neurons from an orangutan-sized hominin ancestor to modern Homo require an additional 360 kcal/d, which is probably not readily available to great apes on their diet.
It has been proposed that the advent of the ability to control fire to cook foods, which increases enormously the energy yield of foods and the speed with which they are consumed (92, 93), may have been a crucial step in allowing the near doubling of numbers of brain neurons that is estimated to have occurred between H. erectus and H. sapiens (94). The evolution of the human brain, with its high metabolic cost imposed by its large number of neurons, may thus only have been possible because of the use of fire to cook foods, enabling individuals to ingest in very little time the entire caloric requirement for the day, and thereby freeing time to use the added neurons to their competitive advantage.
It has been proposed that the advent of the ability to control fire to cook foods, which increases enormously the energy yield of foods and the speed with which they are consumed (92, 93), may have been a crucial step in allowing the near doubling of numbers of brain neurons that is estimated to have occurred between H. erectus and H. sapiens (94). The evolution of the human brain, with its high metabolic cost imposed by its large number of neurons, may thus only have been possible because of the use of fire to cook foods, enabling individuals to ingest in very little time the entire caloric requirement for the day, and thereby freeing time to use the added neurons to their competitive advantage.
The remarkable, yet not extraordinary, human brain as a scaled-up primate brain and its associated cost
In a letter published in American Journal of Clinical Nutrition in 2000, Katharine Milton pointed out:
The technologic abilities of humans derive from their unusually large, complex brain, a brain that, under normal conditions, is fueled by a steady supply of glucose. Consumption of digestible carbohydrate is the most efficient way for humans to obtain glucose for brain function. Potential alternatives--gluconeogenesis or the use of ketones to fuel the brain--represent alternative, more costly metabolic solutions.
Reply to L Cordain et al
Zucoloto’s 2011 review in Psychology and Neuroscience provides further details:
Evolution of the human feeding behavior
The human species is not adapted to the consumption of large amounts of animal (i.e., protein-rich) feeding sources to meet their energy needs because serious renal and hepatic problems can occur from high neoglucogenesis. Proteins are formed by amino acids that have, as their basic structure, the chemical elements carbon, hydrogen, oxygen, and nitrogen, with some exceptions, such as the insect chitin. To liberate energy, the organism uses carbohydrates and lipids. If they lack these substances, then they use amino acids. To utilize amino acids as an energy source, the organism must remove nitrogen through a process known as deamination. Thus, an amino acid molecule without nitrogen atoms can be metabolized or transformed into glucose and metabolize. In the human species, this metabolic process, known as neoglucogenesis, occurs in the liver, and the excess nitrogen must be excreted. This causes a work overload, which can seriously affect the liver and kidneys (Sackheim & Lehman, 2001).
http://psycnet.apa.org/journals/pne/4/1/131.html
In Milton’s 1999 paper, after noting the variety of ways that humans are biologically distinguished from carnivores, she discusses some of the known detrimental effects of high-protein diets on non-carnivores. Ultimately she points out that “adult humans apparently cannot catabolize sufficient protein to meet more than 50% of the daily energetic requirements.”
I don't think there's much grounds to arguing that humans can't thrive on a diet including meat. They certainly can. In our evolutionary history, the availability of meat has likely been of some significance. But right now, most of us are in a situation where we ain't gotta eat meat to live healthily, where we can get all our energy, protein etc needs without eating meat, and where abstaining from it is helpful in reducing animal and human suffering and alleviating environmental degradation.
I think we are naturally omnivores but through choice we can evolve and become healthy vegetarians if our morality so chooses.
I think the days of Homo Erectus when 'high calorie' meant 'good' are well behind people living in first and second world nations where 'low calorie' now means good..
I think the days of Homo Erectus when 'high calorie' meant 'good' are well behind people living in first and second world nations where 'low calorie' now means good..
buddhist
Well-Known Member
Pretty much anything can be a choice.
Because our method of hunting doesn't involve any of that. Same reason wolves don't have the sharpest teeth or claws. We run an animal to death. Most animals are far faster than we are. But we can do this much longer, and literally run something to exhaustion. It just collapses and it's a simple matter to finish it off when you get there.
This is another reason we domesticated dogs; our variant of this works great in the heat, but in the cold it's not as effective. But wolves? They're the opposite. Their form of endurance hunting works particularly well in the cold.
This is how we conquered the planet.
I didn't vote because I think it can be multiple answer . You can choose to eat a vegetarian diet and be a vegetarian based on your personal choice and also be biologically classified as an omnivore.
Yes, as long as a human can avoid the cancers associated with eating meat, and the high cholesterol, and the increased mortality, and make sure that the meat is well-cooked since humans, unlike all animals biologically adapted to eat other mammals, have a gastric pH too high to kill deadly bacteria found in animal flesh, s/he can thrive on such a diet--that is, s/he will certainly obtain adequate calories from that diet..
Most humans who've ever lived, by a massive margin, have done so.
Define “omnivore”.
Obviously, if one doesn't have a biologically based definition, then, in the case of humans (at least), it's meaningless and erroneous to claim that humans are omnivores, as it would just mean that some humans choose to eat other animals. It would not be true to say that all of the humans who do not choose to eat other animals are omnivores.
Humans do not choose to be unable to synthesize vitamin C and therefore need to consume vitamin C daily from an external source. As has been noted by numerous scientists et al., hominids' inability to synthesize vitamin C indicates a long dependence on plant foods that furnish vitamin C. Obviously, humans do not have any biological adaptations resulting from a long history of dependence on eating animals.
I'm sorry i think I interpreted the op differently/wrongly and did not give your post credit for its relevancy . I still stand by my comments of it having nothing to do with what we do now though .
Mammals classified as herbivores have teeth and a digestive system by which they can extract calories and nutrients from animal flesh.
Humans who have diet consisting of a significant percentage (>40%) meat do not survive as long as humans who eat a plant-based diet.
Where did you get that idea? Prove it.
Millions upon millions of house cats have lived their entire lives on Meow Mix, whose primary ingredient is corn, and has very little animal matter in it. They have teeth than can chew it, and they have a digestive system by which they can extract the calories and nutrients from it.
As far as I know the majority of humans who eat a diet consisting of a significant percentage of meat do not avoid the cancers and heart disease associated with that diet.
And humans who eat a diet consisting of a significant percentage of animal matter do not survive as long those who eat a diet consisting of plant foods.
Right. But most humans have lived during times where other things would kill you first anyway, and where small amounts of meat would fit well in your diet. Nowadays we have the capability to avoid causing the suffering which meat-eating inflicts so we can modify our diets to exclude meat if we have that luxury. We must be conscious of the fact that the option of being a vegetarian is a privilege not all are afforded.
What the hell are you talking about? Name any occasion when a human has "run an animal to death". When has that ever happened, ever? Show us a video of that happening.
(If it has ever happened, it obviously wasn't a meat-eater.)
That's the standard practice of the San bushmen and the Raramuri people of Northern Mexico to this day.
Here's a video.
Something like 94% of all humans who have ever lived are alive today.
I have no idea what that is supposed to mean. If someone or some economic system has made it a "privilege" to eat the diet that humans are biologically adapted to eat and remain healthy, it doesn't change the biological facts.
Anyway, it's obviously much more economical for humans to grow the grain and eat it themselves than to raise it and feed it to animals, only a small portion of whose mass is eaten.
It's actually a little under 10%. There've been more or less 108 billion people to have lived, and the world population today is about 7.5 billion. How Many People Have Ever Lived on Earth?
Humans are opportunists, we can thrive on a diet with or without meat. We are able to digest meat and live on it, meaning we have evolved to be able to eat it if the need arises. The need does not arise for most Westerners, East Asians, Latin Americans etc, but they do it anyway which is in my view morally unjustifiable.
Yes, it is more economical. Not only is it more economical, it frees up more land and enables us to better deal with global nutrition problems. Eating meat contributes to starvation globally, as well as water shortages, environmental degradation, what have you.
Then after "running the animal to death," he had to use a spear to kill it.
Can you run such an animal to death? If such running endurance is a biological adaption of omnivory in humans, then the vast majority of humans have lost that adaptation.