Physically at puberty humans can have sex (according to nature). The laws try to take into consideration mental development (isn’t just the physical make up of the brain.) There is also general level of education and mental maturity (non physical aspect of the mind).

These are all subjective. The age of consent has increased with lifespan and education over the years. When i was 14 the age of consent was 14 in Canada now its 16.

I used the term mind, because its not just physical (as western science tends to view the world) its also knowledge/mental maturity.

I don’t plan to check article again for reply. Laws reflect the values of society or the corporations that pass them. The age of consent is more related to societies values (in general) where economic laws more likely reflect the interest of corporations.

Society in general says its wrong for adults to have sex with children. Personally I agree, there is no longer a need to have children at a young age life spans have increased 3 times+ on average over the last few hundred years. The gap between an adult and child in term knowledge is huge today relative to the past.

I find that one puzzling as well. Generally speaking, mental and physical growth differs between individuals and the onset of adolescence can be hastened or delayed by many external factors as well as pure genetics.

Physical development can be retarded by extreme sports or arts (ballet dancing, gymnastics) so even an 18-year old wouldn’t fit the “sexually mature” criteria physically.

Similarly some individuals are precocious and could be considered fully mature far earlier.

Barring any one-size-fits-all solution all you can do realistically is to set a barrier which provides a good compromise between child protection and proportionality of enforcement.

Setting the age to 21 or even 18 means a very large proportion of your citizenry will in their teens or as early adults have been either abuse victims or pedophiles de jure.