Similarly to having people have skills, it would be cool if they had organs and a basic medical system. While they can be ignored by the player, if they’re micromanaged they would provide better tribe performance. Things which could be affected by what the person trains in, what they eat, injuries and genetics. Examples:
Muscles: simple introduction to the player about people’s health. Can specialize in strength, and or fine motor skills (like crafting). Like all others, this could be affected by age and diet.
Heart and lungs: affects tasks that require stamina, impact the health of other organs. (Genetics examples, cardiac malformations, asthma). This could be a simple concept to introduce to the player that health matters for basic performance enhancement if they wish to micromanage it.
Brain: affected by experience - can develop anxiety/depression/apathy/social impairments etc. depending on what you expose them to. It can be useful to have apathetic warriors, anxious hunter gatherers, and the depressed will be more likely to survive illnesses and trauma. These could provide a way to further micromanage a tribe’s specialties, or avoid unwanted problems.
(Genetics could be hard to implement without offending people)
Liver and kidneys: trained and damaged by herbs, poisons, drugs, and dietary quality (carbs/fats/proteins/vitamins and minerals). Can be used to complicate people’s required diet for micromanagement of health and peak performance.
(Genetics examples, diabetes 1 and 2)
You could later introduce diseases and medical procedures: infections, amputations, organ transplants, blood transfusions with blood types, etc. Also therapy, training and remedies for enhancements.