# Were Tyrannosaurus Rex's forearms useless? **URL:** \ **Category:** Factual Questions\ **Created:** [April 7, 2015, 4:22am UTC](https://boards.straightdope.com/t/were-tyrannosaurus-rexs-forearms-useless/717020 "2015-04-07T04:22:29Z")\ **Posts on this page:** 9\ **Page:** 3
**Author:** ![outlierrn](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/outlierrn/32/3005_2.png) [@outlierrn](https://boards.straightdope.com/u/outlierrn)\ **Post date:** [April 14, 2015, 6:32am UTC](https://boards.straightdope.com/t/were-tyrannosaurus-rexs-forearms-useless/717020/41 "2015-04-14T06:32:23Z")
Nature finds a way. ---
**Author:** ![Leo\_Bloom](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/leo_bloom/32/10377_2.png) [@Leo\_Bloom](https://boards.straightdope.com/u/Leo_Bloom)\ **Post date:** [April 14, 2015, 12:40pm UTC](https://boards.straightdope.com/t/were-tyrannosaurus-rexs-forearms-useless/717020/42 "2015-04-14T12:40:37Z")
> [@marshmallow](#): > > … it’s possible the males had a long prehensile penis to bridge the gap (like the aforementioned duck penis). A) Yay, I get to ask/say this again in SD!.. Which (non-extinct) animal has the longest penis relative to body length? Hint:It’s apropos. The question, that is. Although that never stopped me before for telling this fact to anyone, anytime. B) I wanted to look up how long T. Rex lasted as a species compared to us, so I could make an additional joke about T. Rex’s inability to masturbate being the reason. Alas, that jewel of humor is not to be, or at least not as pithy, because I couldn’t think of the word for “last as a species” and the joke wasn’t worth more than two Google scans. Anyone want to try? ---
**Author:** ![Learjeff](https://avatars.discourse-cdn.com/v4/letter/l/94ad74/32.png) [@Learjeff](https://boards.straightdope.com/u/Learjeff)\ **Post date:** [April 14, 2015, 2:58pm UTC](https://boards.straightdope.com/t/were-tyrannosaurus-rexs-forearms-useless/717020/43 "2015-04-14T14:58:04Z")
Do truly vestigial organs last? I’m just guessing here, and would appreciate anyone with actual knowledge of the subject chiming in. But my layman’s guess would be that for the most part, complex and costly organs would degenerate over time, if they had no function at all. We have to keep in mind the fact that “vestigial” doesn’t mean “useless” but rather, that it no longer has much of its original function (e.g., appendix in humans). No doubt there are some useless vestigial structures, such as the phalanges buried in a whale’s flesh at its hips (or something like that). If my guess is correct, though, these are things we see now in existing animals, but if we were to review the fossil record we’d see a fairly pronounced progression of reduction/simplification. What I’m getting at here is that I believe we have a pretty fair number of T. Rex skeletons, with the same arm dimensions, over the duration of T. Rex in the fossil record. That implies to me that they serve some purpose; otherwise we’d see them in a state of flux, or not at all. But is that how evolutionary biologists actually think? Please fight my ignorance. I admit this tends to oppose the vague idea I get from Punk Eek, that in the fossil record we tend to see samples of large populations stabilized by genetic drift, rather than samples of small populations of transitional forms. But even in a large population stabilized by genetic drift (and a stable ecological niche) wouldn’t useless organs tend to fade gradually? ---
**Author:** ![Darwins\_Finch](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/darwins_finch/32/20304_2.png) [@Darwins\_Finch](https://boards.straightdope.com/u/Darwins_Finch)\ **Post date:** [April 15, 2015, 2:13am UTC](https://boards.straightdope.com/t/were-tyrannosaurus-rexs-forearms-useless/717020/44 "2015-04-15T02:13:06Z")
> [@Learjeff](#): > > What I’m getting at here is that I believe we have a pretty fair number of T. Rex skeletons, with the same arm dimensions, over the duration of T. Rex in the fossil record. That implies to me that they serve some purpose; otherwise we’d see them in a state of flux, or not at all. _Tyrannosaurus rex_ fossils “only” span about 2 million years; not really long enough to spot any significant trends (especially none that can be sussed out from individual variation; we have a relatively small sample size of _T. rex_ fossils to work from - only around 50 individuals out of that entire 2-million-year span). Pretty much all fossil species have a more-or-less static morphology in the fossil record – indeed, that’s why they get assigned to a given species, rather than a new species or genus, in the first place. The overall trend among tyrannosauroids shows a reduction in the size of the arms while increasing the size of the overall body, legs, and skull. This indicates that the forearm reduction trend was probably a developmental shift, rather than an adaptive shift. ---
**Author:** ![Leo\_Bloom](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/leo_bloom/32/10377_2.png) [@Leo\_Bloom](https://boards.straightdope.com/u/Leo_Bloom)\ **Post date:** [April 15, 2015, 4:49am UTC](https://boards.straightdope.com/t/were-tyrannosaurus-rexs-forearms-useless/717020/45 "2015-04-15T04:49:15Z")
> [@Leo\_Bloom](#): > > …I wanted to look up how long T. Rex lasted as a species compared to us, so I could make an additional joke about T. Rex’s inability to masturbate being the reason. > > Alas, that jewel of humor is not to be, or at least not as pithy, because I couldn’t think of the word for “last as a species” and the joke wasn’t worth more than two Google scans. > > Anyone want to try? > [@Darwins\_Finch](#): > > _Tyrannosaurus rex_ fossils “only” span about 2 million years; not really long enough to spot any significant trends … OK, joke’s getting closer: we have 2 million years. **Darwin’s Finch** oh **Darwin’s Finch** is there a word for that figure of evolutionary lifespan of a species? I don’t even care about the damn joke any more. It’s a question of English Nounage. Is it “evolutionary lifespan?” ---
**Author:** ![jimbuff314](https://avatars.discourse-cdn.com/v4/letter/j/c57346/32.png) [@jimbuff314](https://boards.straightdope.com/u/jimbuff314)\ **Post date:** [April 15, 2015, 5:49am UTC](https://boards.straightdope.com/t/were-tyrannosaurus-rexs-forearms-useless/717020/46 "2015-04-15T05:49:41Z")
Wiki article on “Background Extinction Rate” has a chart titled “Species Average Lifespan”, measured in millions of years. These are averages of taxonomies like “All Invertebrates”, “All Marine Invertebrates”, “All Marine Animals”, etc. The Wiki article on “Extinction” also refers to the average species lifespan. So I’m guessing “species lifespan” is the go-to. Sorry it’s not more esoteric, I know you value that. ---
**Author:** ![Blue\_Blistering\_Barnacle](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/blue_blistering_barnacle/32/3386_2.png) [@Blue\_Blistering\_Barnacle](https://boards.straightdope.com/u/Blue_Blistering_Barnacle)\ **Post date:** [April 17, 2015, 1:35am UTC](https://boards.straightdope.com/t/were-tyrannosaurus-rexs-forearms-useless/717020/47 "2015-04-17T01:35:35Z")
Just picked up Scientific American this evening. Big article on tyrannosaurs. Seems they started out about human tall about 170 mya, evolved through various large and small forms, culminating in T. Rex and Tarbosaurus. Eyeballing the graphical species bars for those two biggies, they seem to have lasted about 10 million years. ---
**Author:** ![Leo\_Bloom](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/leo_bloom/32/10377_2.png) [@Leo\_Bloom](https://boards.straightdope.com/u/Leo_Bloom)\ **Post date:** [April 17, 2015, 2:07am UTC](https://boards.straightdope.com/t/were-tyrannosaurus-rexs-forearms-useless/717020/48 "2015-04-17T02:07:30Z")
> [@Leo\_Bloom](#): > > OK, joke’s getting closer: we have 2 million years. > **Darwin’s Finch** oh **Darwin’s Finch** is there a word for that figure of evolutionary lifespan of a species? > > I don’t even care about the damn joke any more. It’s a question of English _Nounage_… ital added My friend suggested that this word, which I kind of like, should by parallel to the other part of speech that merits a noun and be “Nouniage.” Which sounds too Frenchified if you saw it freestanding. I would be prolix in my nouniage during my daily SD badinage, but at times not without persiflage. ---
**Author:** ![Learjeff](https://avatars.discourse-cdn.com/v4/letter/l/94ad74/32.png) [@Learjeff](https://boards.straightdope.com/u/Learjeff)\ **Post date:** [April 29, 2015, 2:33pm UTC](https://boards.straightdope.com/t/were-tyrannosaurus-rexs-forearms-useless/717020/49 "2015-04-29T14:33:15Z")
> [@Darwins\_Finch](#): > > _Tyrannosaurus rex_ fossils “only” span about 2 million years; not really long enough to spot any significant trends (especially none that can be sussed out from individual variation; we have a relatively small sample size of _T. rex_ fossils to work from - only around 50 individuals out of that entire 2-million-year span). Pretty much all fossil species have a more-or-less static morphology in the fossil record – indeed, that’s why they get assigned to a given species, rather than a new species or genus, in the first place. > > The overall trend among tyrannosauroids shows a reduction in the size of the arms while increasing the size of the overall body, legs, and skull. This indicates that the forearm reduction trend was probably a developmental shift, rather than an adaptive shift. Thanks! > [@Leo\_Bloom](#): > > ital added > > My friend suggested that this word, which I kind of like, should by parallel to the other part of speech that merits a noun and be “Nouniage.” Which sounds too Frenchified if you saw it freestanding. > > I would be prolix in my nouniage during my daily SD badinage, but at times not without persiflage. 🙂 Just remember that to be consistent with verbiage, it needs to be excessive. Oh wait, you got that. [Previous page](https://boards.straightdope.com/t/were-tyrannosaurus-rexs-forearms-useless/717020.md?page=2)