Scientists are saying that it was a small step for the Panda to move from a meat diet to a grass diet. The article only refers to differences in the Panda's skull, presumably for better chewing.

I've also heard that the Japanese are able to digest Nori because they have the right gut biome because Nori has been part of their diet and the appropriate bacteria has developed over time.

Does that suggest that if the cellulose of bamboo and other grasses were pre-chewed by mechanical means and the right bacteria were introduced into the human gut that we would likewise be able to digest grasses?

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    $\begingroup$ fresh foods contain the right bacteria, especially if they are fermented of left to get a bit old in the right way. taboulet and grass salad after a few days would contain colonies of bacteria that digest grass and taboulet. $\endgroup$ – com.prehensible May 4 '19 at 6:25
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    $\begingroup$ There are edible varieties of bamboo, which are used in Asian cooking. $\endgroup$ – jamesqf May 5 '19 at 4:55

You might find the answers to a similar previous question interesting:

Human Digestion of Cellulose?

Summary of those answers: It seems that some humans do host cellulose-digesting symbiotic bacteria, and do digest some of their cellulose. According to Cellulose and the Human Gut, finely ground cellulose with low lignin content is most readily digested by humans who host the right bacteria.

  • $\begingroup$ Note if you read the linked answer humans digest an insignificant amount of the cellulse they ingest. The problem is the human gut is to short and has nowhere to house the bacteria to allow long term breakdown. bacterial digestion is slow. $\endgroup$ – John May 4 '19 at 16:51
  • $\begingroup$ Hi John. You might find the paper I linked interesting. In some cases - e.g. the digestion of cabbage in some individuals - it appears that up to 75% of the cellulose was digested. $\endgroup$ – Andrew Klaassen May 5 '19 at 18:11
  • $\begingroup$ The only paper you link is about tiny amounts of a single type of purified cellulose It does refer to a paper that has little to do with digestion, cellulose need to be broken down and absorbed, that study never controlled for large intestine breakdown which is not absorbed. this is why some animals like rabbits use coprophagia to digest cellulose. Cabbage is also a domesticated crop with low fiber content. $\endgroup$ – John May 5 '19 at 21:31

No there is something else missing besides bacteria

humans often already have the right bacteria but they don't digest most of the cellulose they ingest because digesting cellulose with bacteria is SLOW. Too slow to keep up with normal mammalian digestion. You need a specialized gut that either has a large complex stomach to keep recycling the cellulose in the system (foregut fermenters) or has large storage chambers to keep the cellulose a long time and allow it to be digested slowly (hindgut fermentation).

humans have neither. To make matters worse Humans have huge caloric needs compared to other animals of the same size. Brains are calorie hogs and our brains are so large they consume 1/4 of all our calories. That is 3 pounds of our mass consumes a quarter of all the calories we eat. honestly without the advent of cooking (which drastically improves the caloric availability of food) human brains could never have reached the size they did.

Further reading

More further reading

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    $\begingroup$ What about panda bears? Do they have said requisites? $\endgroup$ – Ruminator May 4 '19 at 17:01
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    $\begingroup$ Just barely, that would by why they have to eat so much compared to other herbivores, bears already have a longer digestive track than humans, and the giant panda has expanded the stomach and intestines further. but they are still only able to barely survive. theguardian.com/science/2015/may/19/… Note human have a much higher caloric demand than an bear of the same size our brains are calorie hogs. $\endgroup$ – John May 4 '19 at 17:11

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