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Jack is fit and healthy, his body appearing as one of a man in his late 30s to early 40s who's in good physical condition. He spends a lot of time running and is very strong.
He's suffered countless injuries over his life, but the only scars he bears are those from things that happened before he become immortal; there is no canonical detail of any such injuries, but there would be at least some scars from blaster-type weapons.
Jack's physiology differs from a 21st century human in a few ways:
Although Jack is immortal, having accidentally been turned into a paradoxical fixed point in time and space, he can still become ill and can still be injured.
He heals from dying in anything from a few minutes to a few days. In some circumstances, he will not die rather than dying and reviving (e.g. poison gas or radiation exposure).
More minor injuries take longer to heal, but still heal faster than an ordinary human.
He's suffered countless injuries over his life, but the only scars he bears are those from things that happened before he become immortal; there is no canonical detail of any such injuries, but there would be at least some scars from blaster-type weapons.
Jack's physiology differs from a 21st century human in a few ways:
- DNA that's a mixture of human and alien due to the interbreeding of species that has occurred by the 51st century in his timeline
- His pheromones are more highly developed and therefore stronger than those of 21st century humans
- Because he's been a companion of the Doctor and travelled time and space quite extensively, his lymphocytes are mutated by radiation found in the Time Vortex
- This makes his immune system highly effective.
Although Jack is immortal, having accidentally been turned into a paradoxical fixed point in time and space, he can still become ill and can still be injured.
He heals from dying in anything from a few minutes to a few days. In some circumstances, he will not die rather than dying and reviving (e.g. poison gas or radiation exposure).
More minor injuries take longer to heal, but still heal faster than an ordinary human.