3 ms·

Why couldn't we evolve the ability to digest cellulose directly like cows, instead of going through cows? My guess: grazing takes extremely long and so we let

Why couldn't we evolve the ability to digest cellulose directly like cows, instead of going through cows? My guess: grazing takes extremely long and so we let cows do the boring job of grazing outside all day then we quickly slurp up whe harvested calories in just a few glasses of milk.

readams 6y ago
Cows have to go through quite a lot to make it happen, with a multistage digestion process, multiple stomachs, regurgitation and additional chewing of food, the right microbiome. In short it's not an easy trait to just "evolve". Lactose tolerance on the other hand is just retaining a trait into adulthood (lactase production) usually lost after weaning.
- restalis 6y ago
  "Cows have to go through quite a lot to make it happen, with a multistage digestion process, multiple stomachs, regurgitation and additional chewing of food, the right microbiome. In short it's not an easy trait to just «evolve»." The complexity of digestive apparatus found in Bovidae family and other ruminant mammals is just an optimization. Herbivore monogastric mammals like horses consume cellulose too. There even isn't that necessary for the mammal to be (specialized) herbivore in order have the cellulose digesting ability, as pigs clearly demonstrate. Some extensions in our menu limits are always welcomed. Digesting lactose as adults was nice, but digesting cellulose, even if not that pleasant or efficient, would have been even nicer, as when things went historically bad, it would had came in handy if we could literally just run to the forest for more than to just hide.
as-j 6y ago
Why wouldn’t we?? Have you seen a cow? :) An enzyme to break down milk seems to be such an easier adaptation compared to a whole series of stomach, which are basically a series of fermenters. Having raised goats the size of their rumens to body is pretty amazing.
- bonoboTP 6y ago
  Couldn't we have invented some way of doing all that cow-stomach stuff in a pot? Like cooking, grinding, fermenting etc, similar to how we turn other inedible plant stuff like wheat into yummy stuff like bread?
  - jaggederest 6y ago
    You can convert cellulose into glucose but it takes things like this (special cultured bacteria, extremely processed cellulose, and an ultrafilter to remove glucose to drive the reaction): https://onlinelibrary.wiley.com/doi/abs/10.1002/bit.260220806 https://onlinelibrary.wiley.com/doi/abs/10.1002/bit.26022080... Or strong acids and 190°C over a catalyst. Cellulose is remarkably strong, especially with lignin in the structure too. We're lucky anything can digest it at all. Which brings me to mycology, probably the best way to extract energy from cellulose for humans. Sterilize, inoculate, keep moist, and harvest a significant percentage of the source material as good carbohydrates and protein.
    - bluGill 6y ago
      My understanding is cows don't digest cellulose either. They have those stomachs to provide an environment for bacteria that can to live. Cows then digest that bacteria. Which is digestion of course, but it isn't that cows can do it. Our large intestine does the same thing but it isn't anywhere near big enough to get a significant amount of energy from cellulose.
      - pvaldes 6y ago
        Seeing cows as bacteria eaters is a challenging but powerful image. Really clever point.
pvaldes 6y ago
We don't have the right kind of tooth to graze

readams 6y ago

Cows have to go through quite a lot to make it happen, with a multistage digestion process, multiple stomachs, regurgitation and additional chewing of food, the right microbiome. In short it's not an easy trait to just "evolve". Lactose tolerance on the other hand is just retaining a trait into adulthood (lactase production) usually lost after weaning.

restalis 6y ago
"Cows have to go through quite a lot to make it happen, with a multistage digestion process, multiple stomachs, regurgitation and additional chewing of food, the right microbiome. In short it's not an easy trait to just «evolve»." The complexity of digestive apparatus found in Bovidae family and other ruminant mammals is just an optimization. Herbivore monogastric mammals like horses consume cellulose too. There even isn't that necessary for the mammal to be (specialized) herbivore in order have the cellulose digesting ability, as pigs clearly demonstrate. Some extensions in our menu limits are always welcomed. Digesting lactose as adults was nice, but digesting cellulose, even if not that pleasant or efficient, would have been even nicer, as when things went historically bad, it would had came in handy if we could literally just run to the forest for more than to just hide.

as-j 6y ago

Why wouldn’t we?? Have you seen a cow? :) An enzyme to break down milk seems to be such an easier adaptation compared to a whole series of stomach, which are basically a series of fermenters. Having raised goats the size of their rumens to body is pretty amazing.

bonoboTP 6y ago
Couldn't we have invented some way of doing all that cow-stomach stuff in a pot? Like cooking, grinding, fermenting etc, similar to how we turn other inedible plant stuff like wheat into yummy stuff like bread?
- jaggederest 6y ago
  You can convert cellulose into glucose but it takes things like this (special cultured bacteria, extremely processed cellulose, and an ultrafilter to remove glucose to drive the reaction): https://onlinelibrary.wiley.com/doi/abs/10.1002/bit.260220806 https://onlinelibrary.wiley.com/doi/abs/10.1002/bit.26022080... Or strong acids and 190°C over a catalyst. Cellulose is remarkably strong, especially with lignin in the structure too. We're lucky anything can digest it at all. Which brings me to mycology, probably the best way to extract energy from cellulose for humans. Sterilize, inoculate, keep moist, and harvest a significant percentage of the source material as good carbohydrates and protein.
  - bluGill 6y ago
    My understanding is cows don't digest cellulose either. They have those stomachs to provide an environment for bacteria that can to live. Cows then digest that bacteria. Which is digestion of course, but it isn't that cows can do it. Our large intestine does the same thing but it isn't anywhere near big enough to get a significant amount of energy from cellulose.
    - pvaldes 6y ago
      Seeing cows as bacteria eaters is a challenging but powerful image. Really clever point.

pvaldes 6y ago

We don't have the right kind of tooth to graze