What is lactose and where is it primarily found?
Lactose is main carbohydrate (sugar) in milk. It provides energy for young mammals, including human infants.
What is lactose chemically made from?
Lactose is a disaccharide made from glucose and galactose
What enzyme breaks down lactose in the small intestine
Lactase
What happens if lactose is not broken down in the small intestine
It passes into the colon undergoes, bacterial fermentation, produces gases (CO2, methane) which caused bloating cramping, abdominal pain and pulls water into the bowel, causing diarrhoea
What is lactase non-persistence
The ancestral condition were lactose production decreases after childhood leading to lactose intolerance
What is lactase persistence?
The continued ability to digest lactose in adulthood due to mutations, keeping the lactase gene active
How did lactase persistence evolve?
Multiple mutations independently arose in Europe east and North Africa due to dairy farming and cattle herding (convergent evolution)
Why did lactase persistence evolve around 10,000 years ago?
Humans, domesticated, cattle, sheep, and goats, milk consumption created selective pressures, favouring mutations for lactose persistence (gene, cultural evolution)
How does fermentation help lactose intolerant individuals consume milk products?
Lactic acid bacteria ferments lactose into lactic acid, reducing lactose content and gas production making yoghurt and cheese is here to digest
Name key nutrients in milk that provide evolutionary advantages
Calcium, vitamin D, protein, vitamin A, vitamin B12, riboflavin, energy, and fat
Why was milk especially valuable in northern latitude?
Because there is less sunlight so lower vitamin D, which reduces calcium absorption. Milk provided essential calcium for bone health.
What is ethanol and how is it produced naturally?
Ethanol is produced by yeast fermenting sugars in fruits or grains
Why did early apes evolve, improved ethanol metabolism?
A mutation around 4 million years ago, allowed apes to metabolize ethanol from fermented fruit without getting dangerously drunk, reducing fall risk in trees
Which enzymes metabolize alcohol in humans
Alcohol dehydrogenase (ADH) convert ethanol into acetyldehyde (toxic)
Aldehyde dehydrogenase (ALDH) converts aldehyde into acetate (nontoxic)
What happens if ALDH is deficient?
Acetyldehyde accumulate, causing flushing, nausea, rapid heartbeat, headache, and increased risk of alcohol related cancers
Which populations commonly have ALDH2 variants
East Asian populations like China, Korea, Japan, and Taiwan
What is Asian flush?
A reaction to alcohol, including facial, redness, nausea, itchiness, and discomfort due to acetaldehyde buildup from ALDH2 deficiency
How do social and cultural factors influence, alcohol consumption, despite genetic variants?
Cultural expectations, business culture, masculinity, norms, and social pressures can encourage drinking, even if genetics cause unpleasant reactions
Why is lactose intolerance considered a normal human condition?
Because most humans naturally stop producing the enzyme lactase after weaning, lactase persistence is the exception
How do genetic traits shaped traditional diets?
Populations adapt cuisine to food foods they can safely digest (dairy consumption in Europe versus East Asia)
In East Asia they ferment dairy products so they can be digested more easily
How can vitamin B12 intake be maintained in populations with limited meat?
By consuming fermented or pickled foods like kimchi, stinky tofu, or pickled vegetables
What is the selective advantage of lactase, persistence, mutation?
Adult adults who could digest milk had a clean nutrient rich food which contributed to survival advantage
What is the selective advantage of G6PD mutation?
Makes meals less susceptible to malaria
What is the main evolutionary benefit of milk in low sunlight regions
Ensures, calcium, absorption, and prevents crickets/osteoporosis
