Given that the 13th Doctor will be female, we can no longer assume the explanation is that the Doctor is always male. Assuming the in-universe explanation is not just that it was pure chance since it would be overwhelmingly unlikely that the first twelve Doctors would all be male,

What is the in-universe explanation for why the Doctor was male twelve out of thirteen times?

We need not go into the out of universe reasons.

  • 2
    Regeneration. It's a lottery Commented Jul 19, 2017 at 15:02
  • 17
    Because he was born male? Perhaps birth gender weighs the odds heavily for that side.
    – amflare
    Commented Jul 19, 2017 at 15:03
  • 5
    Fun fact: Sydney Newman told the BBC to give the role to a woman back in 1986, but the BBC refused and gave the role to Sylvestor McCoy instead. Commented Jul 19, 2017 at 15:05
  • 6
    This may well get explained in the next series... Commented Jul 19, 2017 at 15:09
  • 3
    Even if it were pure chance, 1 in 2^12 isn't really that rare. If there's 7 billion time lords, like there are 7 billion people, there's almost 2 million of them kicking around in their 12th straight regeneration to the same sex. Commented Jul 20, 2017 at 0:15

4 Answers 4


I don't think there is a lot of in universe reasons. But I'll try to give some

Even though Regeneration is a lottery, some control over it seems to be possible

The best example is given during the Melody -> River regeneration, where she says to "Focus on a dress size".

We have one other example of one Timelords/ladies tend to keep the same sex

In Hell Bent, The General goes into regeneration and goes from male to female. (I'm using neutral to talk of the character for obvious reasons)They then says that they are "Back to normal". Which supposes that the character consider the female sex to be their classical state. Moreover, they say (before this one) having 6 regeneration left.

So we can assume that this character has known a lot more female incarnation then male incarnation, and would not be target to the out of universes reasons.

The Master also has a lot of male incarnations, but here, out of universe reasons might (probably) apply

  • 25
    I remember a conversation (I think in the first Capaldi season) where the Doctor was told that his new regeneration form suits what his own subconscious thinks he needs. E.g. Smith was sillier because Tennant had been too serious, Capaldi was old so that his companions would not fall in (romantic) love with him like they did with Smith. Similarly, his subconscious may never have considered changing gender by merit of having a "male brain", but e.g. seeing the Master as a woman may have opened his subconcious to the idea of becoming a woman.
    – Flater
    Commented Jul 19, 2017 at 16:06
  • 18
    Then the real question is: Why isn't the doctor a ginger? Commented Jul 19, 2017 at 17:25
  • 4
    Yeah. I always just assumed that the Doctor liked being male (and British), this being a preference that he had picked up due to hanging around in Britain a lot. While he couldn’t totally control his regenerations, his preferences influenced them to some extent. Similar with the Master usually being male and the General usually being female, as you mentioned. Some Time Lords, such as the Corsair, might have a more even split.
    – Adamant
    Commented Jul 19, 2017 at 18:09
  • 13
    Don't forget we've seen Romana directly choosing a specific body while regenerating, trying on multiple bodies in the process, but choosing one which looks identical to someone she has recently seen. This implies she had complete control of the body into which she regenerated. Perhaps how much control they have varies based on how prepared they are for the regeneration and/or if the regeneration is due to their choice vs. if the regeneration is because they must regenerate in order to survive.
    – Makyen
    Commented Jul 19, 2017 at 18:20
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    Re the General: immediately after regenerating, she explicitly says, "Oh, back to normal, am I? The only time I've been a man, that last body. Dear Lord, how do you cope with all that ego?" Perhaps she wanted to become a man for the Time War?
    – Rand al'Thor
    Commented Jul 19, 2017 at 23:02

This answer is not explicitly canonical, but it is worth noting as it may very well be the explanation.

The Monte Carlo fallacy states that no amount of previous outcomes in a randomized event will predict the outcome of that randomized event.

For example, if I were to flip a coin 100 times, we could expect the outcome to be roughly 50 flips landing on heads and 50 flips landing on tails. So if we now say that after 50 flips I have only gotten heads, will the 51st flip be tails? Not necessarily, because the chances of the coin landing on tails is 50% EVERY FLIP.

If we apply this to the Doctor, every time the Doctor regenerates, there is a 50/50 chance of male or female. The fact that the 13th regeneration is the first time that female was the result is statistically speaking no more or less remarkable that any other pattern of outcomes because every time there is a regeneration, the chances of the result being male or female remain the same.

Again I must stress, this answer does not detail some canonical information as there may not yet be any, but this is not an out of universe answer as the Monte Carlo fallacy exists both in this universe and (presumably) in the Whoniverse as well.

  • 17
    "If we apply this to the Doctor, every time the Doctor regenerates, there is a 50/50 chance of male or female." Though there's no reason to assume the probability is 50/50 to begin with. Commented Jul 19, 2017 at 17:15
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    We have no evidence that regenerations aren't influenced by previous regenerations. We also don't know that gender is random at all. Not only that, Time Lords can exert conscious control over their regenerations, so I really don't see the point in this answer. Commented Jul 19, 2017 at 17:46
  • 5
    @MagikarpMaster Consider the case of 3 coins. There is one way to get all heads HHH. There are three ways to get two heads, HHT HTH THH. There are three ways to get one head, TTH THT HTT. There is one way to get all tails TTT. Your statement would be true if it were phrased "The chances of getting 12 heads and 1 tails, in that order, are the same as getting 6 heads and 7 tails, in that order." Without considering order, the odds are different.
    – Cort Ammon
    Commented Jul 19, 2017 at 20:28
  • 8
    Because the chance of the Doctor not being female at least one time is a (negation of a) group. All the possible patterns that have the Doctor being female at least one time are in a group. You are comparing the chance of any possible pattern from that group to the single unique pattern of "Male 13 times".
    – DeadMG
    Commented Jul 19, 2017 at 20:45
  • 9
    This answer and all this discussion are so wrong I would downvote ten times and I can no longer remain silent. Why? Because this claims to have a deep understanding but in fact it's the complete opposite. I'm going to call this The Monte Carlo Metafallacy. The Monte Carlo Fallacy is not some magical law of the universe that says that previous outcomes cannot affect future ones. It says that it's true for random uncorellated results as in casino games or coin flips, etc. We have no idea what effects are in play for Time Lord regeneration, and in fact that's what the question is about. Commented Jul 20, 2017 at 5:20

Every answer to this question is inherently speculative (although an official answer may well come with the new series), but my assumption has always been that changing sex is less likely.

That is, Time Lords can regenerate into male or female forms, but changing sex involves a significantly greater physiological change so requires more regeneration energy and is thus less likely. Alternatively, it may be possible only when sufficient damage has occurred to the relevant organs.

If this is true, we would expect 13 to be followed by a string of female Doctors (but a male 14 is also possible).

Some maths: If there is, say, a 10% chance of changing sex at each regeneration (and excluding the metacrisis, but not the War Doctor), a string of 14 male incarnations is the single most likely outcome, with a 23% chance of occurring.

Changing at some chosen time, resulting in N male Doctors followed by 14 - N females, has a probability of only 3%; this includes the position in which we find ourselves now. But there are 13 possible values of N, resulting in a "single change" probability of 33%; this value is more informative.

The probability of there having been more than one change by now is thus 56%.

This implies that a sex change is somewhat overdue, but it is by no means unreasonable that one would not have occurred yet. The probability can, of course, be tweaked to fit reality even better (or according to the writers' whims); a lower probability will make the model fit better.


The honest answer to this question is that we don't know. Until the most recent series's (Timelord General, Corsair comments etc) everything written and shown on tv clearly pointed to Timelord gender being fixed. It is only in the past 5-7 years that the "rules" have been changed to allow a Timelord to change gender.

  • 3
    Wrong. There never was an explicit "rule" saying timelords were gender-fixed. In fact, back in 1981 when Tom Baker finished his stint as The Doctor, he said in an interview "Good luck to the new Doctor, whoever he OR she may be." Commented Jul 20, 2017 at 8:47
  • 2
    Also, "there was never any evidence to the contrary" is not the same as "clearly points to". Commented Jul 20, 2017 at 8:49
  • While it was suggested by Tom Baker outside of the universe until now nothing within the Fiction has suggested it was possible every regeneration has remained same gender until Matt Smiths Dr. I am happy with the decision to make it possible but I think we have to accept that until recently it didn't happen. I hope that early on in the new series the DR explains why this is the first transformation into a female dr.
    – Richard C
    Commented Jul 20, 2017 at 15:25

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