Topic 6 - Evolution

Question 1

Explain the timeline of human evolution from approximately 4 million years they evolved through a series of stages to become modern humans about 200,000 years ago

Answer 1

• Humans evolved in Africa first
• H. habilis –> H. erectus –> H. sapience
• Began hunting (H. erectus) and introduced meat to their plant based diet
• the ability to control fire was a very important step - could defend themselves from predators + cooking

Question 2

What were some good consequences of cooked food (compared to uncooked food)

Answer 2

• hunting less (get more energy form cooked food)
• led to the growing brain
• size of intestine became shorter - cooked food is more digestible so less energy is invested in digesting food (shortening the gastrointestinal system)

Question 3

About 10 thousand years ago, we had the. . .

Answer 3

Agrarian revolution
- humans in different parts of the world started to learn how to farm
- began to form stable societies

Question 4

About 250 years ago, . . .

Answer 4

the Industrial revolution occurred
- food processing was a lot higher
- onset of obesity + diabetes

Question 5

Pleistocene (like 2 million years ago)

Answer 5

hunter-gatherers

Question 6

Holocene (like 10 thousand years ago)

Answer 6

farmer-pastorals

Question 7

Why did a population explosion happen?

Answer 7

The domestication of grains such as sorghum, barley, wheat, corn, and rice created a plentiful and predictable food supply, allowing farmers’ wives to bear babies in rapid succession—one every 2.5 years instead of one every 3.5 years for hunter-gatherers. A population explosion followed; before long, farmers outnumbered foragers.

The notion that we stopped evolving in the Paleolithic period simply isn’t true. Our teeth, jaws, and faces have gotten smaller, and our DNA has changed since the invention of agriculture.

Question 8

Explain how these early ancestors became bipedal and shifted their diet from largely plant based to more animal food based (initially through scavenging), due to different food availability in grassland environments.

Answer 8

• bipedalism (ability to walk on 2 legs) evolved 4 million years ago
• Until agriculture was developed around 10,000 years ago, all humans got their food by hunting, gathering, and fishing.
• As farming emerged, nomadic hunter-gatherers gradually were pushed off prime farmland, and eventually they became limited to the forests of the Amazon, the arid grasslands of Africa, the remote islands of Southeast Asia, and the tundra of the Arctic.
• starting to eat calorie-dense meat and marrow instead of the low-quality plant diet of apes, our direct ancestor, Homo erectus, took in enough extra energy at each meal to help fuel a bigger brain.
• The energy freed up as a result of smaller guts could be used by the greedy brain

Question 9

Describe the role of controlled fire in the evolution of the human digestive system.

Answer 9

• fossils show the teeth and digestive tract of Homo erectus DECREASED in size around the same time brain size increased
• this evidence means our ancestors started eating softer, higher-quality foods
• Recent studies further suggest humans have genetic adaptations for eating cooked foods
• Some predate our split from Neandertals
• Did this require changes in our social behavior (sharing)?

Question 10

Reflect on the human characteristic of humans occupying a great variety of habitats and thriving on a very variable diet.

Answer 10

• As the earliest farmers became dependent on crops, their diets became far less nutritionally diverse than hunter-gatherers’ diets.
• Eating the same domesticated grain every day gave early farmers cavities and periodontal disease rarely found in hunter-gatherers
• When farmers began domesticating animals, those cattle, sheep, and goats became sources of milk and meat but also of parasites and new infectious diseases.
• Farmers suffered from iron deficiency and developmental delays, and they shrank in stature.

Question 11

There is tremendous variety in what foods humans can thrive on.

Answer 11

Traditional diets today include the vegetarian regimen of India’s Jains, the meat-intensive fare of Inuit, and the fish-heavy diet of Malaysia’s Bajau people. The Nochmani of the Nicobar Islands off the coast of India get by on protein from insects.

Question 12

Explain human migrations from approximately 60,000 – 80,000 years ago out of Africa to eventually occupy all continents except Antarctica.

Answer 12

• early humans first migrated out of Africa into Asia b/w 2 million & 1.8 million years ago
• entered Europe somewhat later, b/w 1.5 and 1 million years later
• species of modern humans populated many parts of the world much later
• e.g. people first came to Australia within the past 60,000 and to the Americas within the past 30,000 years or so
• the beginnings of agriculture and the rise of first civilizations occurred within the past 12,000 years

Question 13

Explain the introduction of processed food on human health

Answer 13

• so far, studies of foragers like the Tsimane, Arctic Inuit, and Hadza have found that these people traditionally didn’t develop high blood pressure, atherosclerosis, or CVD
• processed foods cause diseases like heart disease, high blood pressure, diabetes, cancer, acne
• And Tsimane people who eat market foods are more prone to diabetes than those who still rely on hunting and gathering

Question 14

Common misconception about Paleo diet

Answer 14

that it was mainly composed of meats

Question 15

Some negative effects of eating red meat based on research studies.

Answer 15

Recent studies confirm older findings that although humans have eaten red meat for two million years, heavy consumption increases atherosclerosis and cancer in most populations—and the culprit isn’t just saturated fat or cholesterol.

• Our gut bacteria digest a nutrient in meat called L-carnitine.
• In one mouse study, digestion of L-carnitine boosted artery-clogging plaque.
• Research also has shown that the human immune system attacks a sugar in red meat that’s called Neu5Gc, causing inflammation that’s low level in the young but that eventually could cause cancer.

Question 16

Mice study on cooked vs uncooked food

Answer 16

• To test his ideas, Wrangham and his students fed raw and cooked food to rats and mice.
• When I visited Wrangham’s lab at Harvard, his then graduate student, Rachel Carmody, opened the door of a small refrigerator to show me plastic bags filled with meat and sweet potatoes, some raw and some cooked. - Mice raised on cooked foods gained 15 to 40 percent more weight than mice raised only on raw food.