Many species in the Star Trek universe have "bumpy foreheads"--most famously, the Klingons.

What are the likely factors that influenced the evolution of Klingon cranial ridges?

Could it be a protective measure against some environmental factor like radiation, or does it serve some other purpose?

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    They looked cool and were not too difficult for the makeup department to apply. I'm sorry, I realise that people want in-canon answers to questions like this, but such answers simply don't exist and can't be checked -- there aren't any peer-reviewed Federation journals of comparative anatomy that we can appeal to, for example. This question is asking for speculation, not for a verifiable answer.
    – Mike Scott
    Jan 30, 2011 at 16:54
  • I like this question. I've been wondering the same thing but never went and looked it up. That said, I have to agree with Rick; it's an easy thing to pull off. Jan 30, 2011 at 19:26
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    @Mike: That would apply to this entire Q&A forum. So I guess we can just shut this site down then? Even if there aren't any scientific journals that can be referenced, there's still the TV shows, movies, and non-canon books and other works that could hint at an answer. Nov 20, 2011 at 4:39
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    @Mike: Your original comment implied that because this is fiction and without real peer-reviewed scientific sources, there's no point in asking it. Besides, as the answers posted have shown, this question is answerable by referencing canonical material. Nov 20, 2011 at 7:26
  • @MikeScott: All of those questions seem to be "out of universe"-questions in the first place, i.e. questions asking about meta information that would not, say, be asked by characters within the universe. As such, those questions constitute only a fraction of this site. Jul 30, 2014 at 8:27

4 Answers 4


It's a sagittal crest. Their cranium is encased in an exoskeleton, which has a tricipital lobe. Perhaps their skull forms from both sides, and the ridges are where the bone fuses?

Source: http://en.memory-alpha.org/wiki/Tricipital_lobe


Check the TNG series for the "Genesis" episode where a synthetic T-cell becomes a viral infection that causes the crew to "de-evolve". Worf's proto-self is not a creature to be toyed with, and the cranial ridge is much more pronounced. As Teknophilia said in another answer, there's an extra skeletal shell around their skull.

Klingons are built to survive, as was mentioned in another TNG episode - "Ethics" (the one where Worf becomes paralyzed from the waist down). The visiting doctor who is working on an experimental paralysis surgery is reviewing Klingon anatomy and remarks offhand that whoever designed them certainly believed in spare parts.


I think there is some thinking going on behind the make-up stying in ST.

As a rule, the more aggressive beings tend to have heavy ridged foreheads, which I have always presumed reflects thicker and heavier bones - the ridging would allow for overall thickness without excessive weight. For beings who like to hit each other a lot, it makes sense that they have developed something there to give some protection against frontal attacks. They thicker skull in other places is probably hidden behind their hair.

Those species who have developed a more Vulcan approach to life seem to have smoother heads, to better fit their larger brain capacity.

It is also significant that heavy forehead makeup tends to make someone look agressive, and smooth features the opposite, probably reflecting out own past developing from Neandethal through to Homo Sapiens.

  • The Talosians' heads are particularly fragile-looking. Nov 1, 2011 at 21:34
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    Ridges also act like ribbing, adding reinforcement without increasing the thickness of the entire cranium. Nov 20, 2011 at 4:55
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    "developed a more Vulcan approach to life" - we were told more than once that Vulcans used to be quite a warlike species in the past. From what we could see on ENT, that seems to have been the case until only a few millennia back (mind you, the Romulans have probably diverged from the Vulcans before that, so that must have been well within the Vulcan spacefaring age), which is not enough time for evolution to have such a visible effect. Jul 30, 2014 at 8:31
  • @O.R. Mapper - My thoughts exactly. And consider also that the Vulcans were telepathic and learned to kill each other with just a thought (if you believe Tallera from TNG: Gambit). So perhaps reduced threat from melee weapons (as compared to non-telepathic species) allowed Vulcans not to develop such a strong cranial protection.
    – Xplodotron
    Jun 22, 2016 at 14:41

In a DS-9 episode where Commander Sisko and Worf travel back in time to the original Enterprise, original series footage of Klingons brawling with crew members is shown. They have no prominent cranial ridges. To the question "Those are Klingons? What happened?", Worf answers, looking rather embarrassed, "It's a long story". This implies that the cranial ridges were of recent origin, at least for Klingons (although from a scriptwriter's standpoint, it was clearly an attempt to address a discrepancy in a scene).

  • You haven't watched Enterprise, have you? Jul 30, 2014 at 8:34
  • I have, but only circa 2012, after I wrote this answer!
    – HNL
    Jul 31, 2014 at 6:23
  • But the devolved Worf from TNG: Genesis did have some serious head protection. So, I think that establishes that Klingons originally evolved from having lots of protective cranial features (proto-Worf in TNG) to having much less pronounced ridges (TOS time) back to pronounced features again (as explained in ENT).
    – Xplodotron
    Jun 22, 2016 at 14:39

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