ROSE: Well, he's got two hearts.
JACKIE: Oh, don't be stupid.
ROSE: He has.
JACKIE: Anything else he's got two of?
(The Christmas Invasion, 2005 Christmas special)

So is there anything else he's got two of? Or to put it more generally, what are the physiological differences between a human and a Time Lord, other than the number of hearts? How can you tell, just from examining a Time Lord's body, that he - or she - is a Time Lord?

Let's say you can't kill the person to see whether they regenerate, nor can you wait hundreds of years to see whether they die of old age. All you can do is a one-off examination of their body. You have all the equipment you need: stethoscopes and so forth. So that you can see the whole of their body (as well as to exclude the possibility of identifying a Time Lord by their dress sense), let's assume they're naked:

naked Doctor

  • 8
    Kill him. If he regenerates, he's guilty of being a Time Lord. If he stays dead... then he was innocent. – Omegacron Jul 15 '15 at 19:01
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    @Omegacron What if he's in his final regeneration (and doesn't have a handy bunch of Gallifreyans behind a crack in the sky to give him a new regeneration cycle)? – Rand al'Thor Jul 15 '15 at 19:08
  • 2
    Easy, by their eccentric dress sense. – Reinstate Monica - Goodbye SE Jul 15 '15 at 19:10
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    @Wikis I've edited to make it clearer what I'm asking. I hope Matt Sith's naked torso isn't considered too NSFW for this site? – Rand al'Thor Jul 15 '15 at 19:40
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    "Matt Sith" ... I'm picking up Star Wars knowledge by osmosis on this site! :-O – Rand al'Thor Jul 15 '15 at 19:40

This is from Wikipedia so take it for what it is, but the main differences are:

Physiological differences from humans include two hearts which normally beat at 170 beats per minute, an internal body temperature of 15 degrees Celsius (59 degrees Fahrenheit) and a "respiratory bypass system" that allows them to survive strangulation. Time Lords can also survive full exposure to the vacuum of space with no ill effects, though when in a vacuum for an extended period, a Time Lord must take a supply of air along or suffocate. Time Lords also seem to have an increased resilience to higher frequencies of sound, as seen in "The Christmas Invasion" and "Partners in Crime". If severely injured, Time Lords can go into a healing coma which lowers their body temperature to below freezing.

So according to this, a simple temperature test will do. If you're still not sure, throw him to outer space and see how long it takes him to suffocate.

Some of these facts are marked as "citation needed". Others are referenced to different episodes of classic Who and new Who.

  • 2
    Does anybody have a source for that body temperature statement? Wikipedia page itself lacks that particular citation. – Viniter Aug 15 '15 at 16:59
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    “Time Lords can also survive full exposure to the vacuum of space with no ill effects” — weeeeell, sometimes they go blind. – Paul D. Waite Feb 14 '18 at 9:28
  • They can also survive freezing temperatures way below human range "DOCTOR: Stasis chamber. You've got to take it below minus two hundred. Freeze it out of me! It'll use me to kill you if you don't." Season 3, Episode 7 (42 minutes) – Matt Jan 8 '20 at 14:21

Assuming a brief (relatively) non-harmful physiological examination with commonly available 21st century human medical tools ...

Aside from the 2 heartbeats... which might not be unique to Gallifreyan physiology, heck even one our own species has had 2 hearts!

Also assuming they haven't had a "dodgy" regeneration and are missing a head or have a dog's nose (according to comments by the 9th Doctor)....

If you stuck a light down their throat you might see evidence of their "Respiratory bypass system".

  • I've always taken that "missing a head" thing to be a case of Rule 1: The Doctor Lies. – Rand al'Thor Jul 15 '15 at 22:04
  • The tricky bit is that the Doctor sometimes tells outrageous truths. – John McNamara Aug 15 '15 at 15:13
  • When you have eliminated the impossible, whatever remains, however improbable, must be the truth. - Sherlock Holmes – Rand al'Thor Aug 15 '15 at 15:14
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    Missing a head is very common. Some Time Lords have as few as one head. These tend to be overrepresented in the military and political arenas of Time Lord society. – Pete Kirkham Mar 29 '16 at 14:04

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