methionine and lysine are essential proteins that are difficult to come by or in tiny amount compare to those amino acid that your body can produce itself or from diet.

"Electricity"? What "electricity"? Animals are powered by chemical reactions, not by electricity. And obligate carnivores such as felines do not seem to lack in energy.

Good question -- but I'd say turf it to biology.

I think it's the other way around: All intelligent beings become true omnivores ;-). It is of course well possible that all wise beings become vegetarians. I for one will stay savage.

@AlexP what electricity? The electricity which flows through our nerves and heart muscles, of course. graduate.umaryland.edu/gsa/gazette/February-2016/… It's why electroencephalogram and electrocardiogram are named what they are.

@RonJohn: What the EEG and EKG measure is a side effect of neurotransmission. It's noise. Our nerves don't want to make it, but the way neurotransmission works it generates electromagnetic noise. (It's like a computer making audible noise. The computer doesn't work by means of mechanical vibrations, but its fans and keys etc. do make them. One can hear the noise and deduce that the computer is idle or busy.) The signals themselves are chemical (at the synapses) or electrochemical (along the dendrites and axons themselves). Nothing is powered by electricity is the human or animal body.

@AlexP you're wrong about it being noise. A quote from the article pasted into my first comment: "in order for the heart to pump, cells must generate electrical currents that allow the heart muscle to contract at the right time. Doctors can even observe these electrical pulses in the heart using a machine, called an electrocardiogram or ECG. Irregular electrical currents can prevent heart muscles from contracting correctly, leading to a heart attack."

@RonJohn: Stop your subscription to that publication and demand your money back. Yes, it is called the electrical conduction system of the heart. No, it does not actually conduct an electrical signal; it conducts an electrochemical signal very similar to the signal conducted by nerves. (The signal consists of an imbalance of ions across a membrane. By necessity, this is accompanied by an difference of electric potential, but the foundation is chemical. The signal propagates at chemical speed, not at electrical speed.)

@AlexP you seem to be laboring under the misimpression that I think there are copper wires and little electric motors in our bodies. Of course there isn't. That does not mean that our bodies don't make and require some electric current.

With a sufficiently restrictive definition of sapience, and based on a sample size of one, sapient species must be omnivores. But ... elephants and gorillas (both herbivores) are quite intelligent, as are octopi and dolphins (both carnivores).

@AlexP Felines spend a lot more time sleeping than humans, though.

@RonJohn: Electrical signals propagate at the speed of light in the transmission medium. Action potentials propagate a hundred million times slower. That is eight orders of magnitude. The two kinds of signals are very obviously not of the same nature.

@AlexP "But the voltage differential is not what the body actually makes". It's irrelevant what our bodies want. What's relevant is what happens. Now stop assuming that we think there are copper wires and little electric motors in our bodies.

There's a lot of space between 'I have to eat some meat' and 'I only eat meat'. Even true carnivores like polar bears are described as having a diet of 90% meat. Also worth noting that a prey animal's body isn't pure protein; the liver contains carbs for quick release into the bloodstream.

What sense does this even make for alien species composed of something other than proteins/fats/organics? What of AI?

@Peter-ReinstateMonica I'll split the difference... how does pescetarianism sound?

I'm new to this particular site but isn't this a question about evolutionary biology? Is it OT?

You need to define "sapience". The comments here seem to confuse "sapience" with "conscience" which is different from "cognition", "perception", and "intelligence" (all related but distinct terms.)

"carbohydrates to turn into electricity" are you sure you heard that correctly?

Even digestion in general is not required for sapience. There are many sources of energy such as photosynthesis or chemosynthesis. Once you have energy, you just need some chemical pathways to creating the brain (or brain-like) structures you need.

@RonJohn If you'd need electricity to generate nerve impulses, and you need to eat some non-meat to generate it, how can carnivores even exist?

@EmilBode nowhere did I write -- or even imply -- agreement with OP's belief about carbohydrates.