The Humpback whales, George and Gracie, were brought back to the future in order to save earth and repopulate the species. How was this accomplished?

While Humpback whales have a life expectancy of 45-50 years, George and Gracie have already used up about half of that life span.

Even considering that Gracie is pregnant (she told Spock), they have a gestation period of 12 months. Humpback calves nurse for approximately six months then mix nursing and independent feeding for possibly six months more. Offspring reach sexual maturity at 6-10 years of age so it would be another decade before another 'mature' whale would even be available. It's difficult to imagine creating a viable population from only two mature adults.

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    A common number for a viable gene pool for a human colony is 160 as a minimum. However, with the genetic techniques and cloning capability, I would gather they could repopulate the oceans with two as a starting point.
    – JohnP
    Commented May 8, 2014 at 22:28
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    I'm still trying to figure out why they needed transparent aluminum. Couldn't they have just used ... aluminum? Or pretty much anything else? Who needs to see the whales while they travel back in time? Commented May 9, 2014 at 2:47
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    @DougMcClean: scifi.stackexchange.com/questions/16053/…
    – Micah
    Commented May 9, 2014 at 3:14
  • Ha ha - the question title reminded me of Scotty's confusion when Kirk tells him they'll need to fill the cargo bay with water. KIRK: Scotty, we've got to find some humpbacks. SCOTT: Humpbacked ...people? KIRK: Whales, Mister Scott, whales!
    – RobertF
    Commented Sep 8, 2016 at 18:23

4 Answers 4


The humpbacks were not brought back to repopulate the species. The main reason they wanted the whales was to answer the probe that was close to Earth and destroying it.

In the movie, a giant probe was moving through space and transmitting a signal which was disabling power to starships as it moved through space. When it reached Earth, the signal had disabled all the power systems on Earth and was causing planetary storms. Spock deciphers that the signal was the call of a humpback whale, so they had to go back in time to get humpbacks to answer the signal.

As far as canon sources, I don't remember them explaining in the movie just how two whales will be able to repopulate a species unless they use futuristic methods like cloning, genetic manipulation, etc.

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    Answering the probe was the primary goal, but Kirk specifically told Gillian Taylor that they intended to repopulate the species. I don't think he was deliberately lying (at the very moment when he was telling her for the first time that he was from the future), but perhaps he hadn't thought things through. And as JohnP's comment suggests, with 23rd century technology they probably could repopulate the species starting with just 2 whales. Commented May 9, 2014 at 0:29
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    Not re-populating the species would just lead to the probe returning to look for them again. Commented May 9, 2014 at 2:02
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    In a way Kirk was lying; he didn't tell her about the Yodel after all. It's a tossup whether a 20th Century biologist would be more likely to believe that in the future angry Yodelers will destroy Earth if they don't hear any whalesong or that two whales is enough to repopulate a species.
    – Kyle Jones
    Commented May 9, 2014 at 2:35
  • Good answer. Answering the probe was the first concern when it comes to transporting the whales to the future. Repopulation was indeed a secondary issue.
    – Morgan
    Commented Feb 12, 2016 at 19:17
  • It makes sense that Kirk telling her they were repopulating as trying to explain an alien probe doing this/that to Earth and who knows what else would have taken too long. Besides, telling someone as passionate about whales as her that they were going to restore their population would be an easy sell.
    – Bilskirnir
    Commented Mar 25, 2020 at 17:24

If you'll accept the Vonda McIntyre novelization as a source, it goes into some detail about this.

Apparently they have frozen humpback tissue on hand that they could clone. However, 1) it won't help with the immediate problem, because a cloned whale won't know any of the songs the probe is looking for, and 2) humpbacks are big-brained enough that they have to learn a lot of stuff from their parents or they won't survive, which is why nobody tried to reintroduce them before.

"If the probe wants a humpback, we'll give it a humpback," McCoy said. "We've reintroduced other extinct species by cloning frozen tissue samples-"  

"The same difficulty remains, Dr. McCoy," Spock said. "The reason great whales have not been reintroduced to earth's seas is that no great whales still exist to teach them survival, much less communication. You could clone a whale, of course-but you would create a lonely creature with no language and no memory of its own culture. Imagine a human child, raised in complete isolation. Imagine. . . my own existence, had you refused to undergo fal-tar-pan. No. A cloned whale, crying its despair, could bring only further destruction. Besides," he said, considering practicality, "I doubt earth could survive for the years it would take to grow a cetacean to maturity."

At the end of the book, the combination of clones with genuine, culturally literate, 20th-century whales is supposed to suffice to repopulate the species, though neither would be enough on their own.

Samples of whale cells, preserved in the twentieth century, would add to the species' genetic diversity through cloning. Legends and myths to the contrary, two individuals-even three, when Gracie's calf was born-were not sufficient to reestablish any species. The whales would never again be hunted, and their freedom would never again be curtailed.

  • I would have to look at that novel. I'm generally skeptical about much of the EU, especially if it goes beyond simply filling in some plot holes and goes hog wild at creating a whole new universe out of whole-cloth. That goes far beyond my scope interest or time to follow the convolutions or creations.
    – Morgan
    Commented May 18, 2014 at 3:26
  • I've taken the liberty of adding in what I think are the appropriate book quotes to supplement your answer.
    – Valorum
    Commented Apr 2, 2018 at 6:53
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    I love the idea of "literate" whales.
    – Jontia
    Commented Apr 2, 2018 at 7:03

You know, now that they did it once, they could just go back in time again and get some more whales. If they go back far enough, they can even avoid having to deal with whale hunters at all.

Normally they wouldn't bother doing any such thing (Temporal Prime Directive), but if the race that sent the probe made it an issue, well....

  • They nearly all died the first time. I doubt that they'd want to try it again.
    – Valorum
    Commented May 26, 2016 at 17:32
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    @Valorum - "They nearly all died" is basically the plot synopsis for every episode of TOS. Except the redshirts, for whom the synopsis was, "Died to 'X' while (defending)/(being watched by) Kirk.
    – Jeff
    Commented Sep 12, 2017 at 15:18

George and Gracie 'could' be used to repopulate the species via say cloning, or artificial insemination to help create new (and large) numbers of the species.

We know cloning is not favorably looked upon in the 24th century as far as Humans go, but, there's nothing to say the same rules apply in the case of bringing back a species from extinction.

Artificial insemination might be the best option with some genetic manipulation to extrapolate the genome and make sufficiently large genetic differentials to avoid potential problems (defects), and possibly with some cloning in the mix too.

  • This is addressed in the answers above. Is there anything additional info that you can add based on evidence we've not already considered?
    – Valorum
    Commented Apr 2, 2018 at 6:54

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