# Dinosaur Extinction **URL:** \ **Category:** Factual Questions\ **Created:** [December 20, 2015, 6:38pm UTC](https://boards.straightdope.com/t/dinosaur-extinction/740940 "2015-12-20T18:38:01Z")\ **Posts on this page:** 20\ **Page:** 3
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [December 21, 2015, 4:27pm UTC](https://boards.straightdope.com/t/dinosaur-extinction/740940/41 "2015-12-21T16:27:23Z")
The common ancestor was \*using tools \*beyond the ability of chimps. I’m not sure exactly when _making_ tools in the sense of chipping flint developed. ---
**Author:** ![MrDibble](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mrdibble/32/114_2.png) [@MrDibble](https://boards.straightdope.com/u/MrDibble)\ **Post date:** [December 21, 2015, 4:41pm UTC](https://boards.straightdope.com/t/dinosaur-extinction/740940/42 "2015-12-21T16:41:40Z")
> [@Colibri](#): > > I’ve been having trouble finding the reference, but I’ve seen statements that for several million years after the event the largest land animal was no larger than a large dog. (I don’t think I’ve ever seen a reference saying the limit was five pounds - maybe five kilos.) [A bit bigger than that, I think](http://boards.straightdope.com/sdmb/showpost.php?p=18744496&postcount=25). But within that order of magnitude in kilos. ---
**Author:** ![John\_Mace](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_mace/32/185_2.png) [@John\_Mace](https://boards.straightdope.com/u/John_Mace)\ **Post date:** [December 21, 2015, 7:07pm UTC](https://boards.straightdope.com/t/dinosaur-extinction/740940/43 "2015-12-21T19:07:17Z")
> [@Chronos](#): > > There were at least three lines of hominids who reached the point of making and using tools (things like clay and flint): Us, Neanderthals, and Floresiens. Granted that we’re all three pretty closely related, but how smart was the most recent ancestor of those three? Did the big jump happen once, from chimplike intelligence to that creature, or did it happen three times, from that creature to the three tool-users? > [@TriPolar](#): > > The common ancestor was \*using tools \*beyond the ability of chimps. I’m not sure exactly when _making_ tools in the sense of chipping flint developed. The common ancestor would have be _H. erectus_ (or some other name, but similar species, depending on the classification scheme you use). _H. erectus_ arose about 1.8MYA. And you forgot the Denisovans, also a descendant. _H. erectus_ made the famous hand axes. The oldest worked stone tools are about 2.5MYA. Chimps use stone tools, but they don’t modify the stones. ---
**Author:** ![Sailboat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/sailboat/32/461_2.png) [@Sailboat](https://boards.straightdope.com/u/Sailboat)\ **Post date:** [December 21, 2015, 7:09pm UTC](https://boards.straightdope.com/t/dinosaur-extinction/740940/44 "2015-12-21T19:09:51Z")
> [@Lawrence\_Cromwell](#): > > Baffled by Science Well, the book [_Science Made Stupid_](http://www.besse.at/sms/smsintro.html) explains that: > [@](#): > > Once, when the secrets of science were the jealously guarded property of a small priesthood, the common man had no hope of mastering their arcane complexities. Years of study in musty classrooms were prerequisite to obtaining even a dim, incoherent knowledge of science. > > Today, all that has changed: a dim, incoherent knowledge of science is available to anyone. ---
**Author:** ![Really\_Not\_All\_That\_Bright](https://avatars.discourse-cdn.com/v4/letter/r/e8c25b/32.png) [@Really\_Not\_All\_That\_Bright](https://boards.straightdope.com/u/Really_Not_All_That_Bright)\ **Post date:** [December 21, 2015, 7:12pm UTC](https://boards.straightdope.com/t/dinosaur-extinction/740940/45 "2015-12-21T19:12:25Z")
What I’ve never understood is why most large _marine_ reptilians also went extinct in the KT event. Shouldn’t the same conditions that protected turtles and crocodilians have saved them too? ---
**Author:** ![John\_Mace](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_mace/32/185_2.png) [@John\_Mace](https://boards.straightdope.com/u/John_Mace)\ **Post date:** [December 21, 2015, 7:21pm UTC](https://boards.straightdope.com/t/dinosaur-extinction/740940/46 "2015-12-21T19:21:16Z")
> [@Really\_Not\_All\_That\_Bright](#): > > What I’ve never understood is why most large _marine_ reptilians also went extinct in the KT event. Shouldn’t the same conditions that protected turtles and crocodilians have saved them too? It is a puzzlement. ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [December 21, 2015, 7:30pm UTC](https://boards.straightdope.com/t/dinosaur-extinction/740940/47 "2015-12-21T19:30:10Z")
They may simply have been unable to adapt to the changed conditions. Turtles and crocodilians are built for survival. ---
**Author:** ![John\_Mace](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_mace/32/185_2.png) [@John\_Mace](https://boards.straightdope.com/u/John_Mace)\ **Post date:** [December 21, 2015, 7:37pm UTC](https://boards.straightdope.com/t/dinosaur-extinction/740940/48 "2015-12-21T19:37:43Z")
> [@TriPolar](#): > > They may simply have been unable to adapt to the changed conditions. Of that, I think we can be certain! 🙂 ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [December 21, 2015, 7:40pm UTC](https://boards.straightdope.com/t/dinosaur-extinction/740940/49 "2015-12-21T19:40:48Z")
To go a little further, turtles and crocodilians can live on the land and in the water, and everything in between. They also have adapted to both salt water and fresh water. They both lay eggs while at least some of the large marine reptiles did not. It could have been only eggs that survived. The disruption of the ecosystem probably cut the food supply severely for large marine predators unless some of them had adapted to deep water hunting in the manner of sperm whales. > [@John\_Mace](#): > > Of that, I think we can be certain! 🙂 Yeah, I realized what that sounded like. I just meant failed to adapt as opposed to got wiped out instantly by the event. ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [December 21, 2015, 8:25pm UTC](https://boards.straightdope.com/t/dinosaur-extinction/740940/50 "2015-12-21T20:25:14Z")
> [@Really\_Not\_All\_That\_Bright](#): > > What I’ve never understood is why most large _marine_ reptilians also went extinct in the KT event. Shouldn’t the same conditions that protected turtles and crocodilians have saved them too? Actually, ichthyosaurs and pliosaurid plesiosaurs were already long extinct by then, having disappeared about 25 million years earlier for unknown reasons. The remaining plesiosaurs and mosasaurs were large, active predators that probably fed on live prey and would have been more susceptible to disruption of the food chain than crocodiles, which can survive as scavengers. In the case of the mosasaurs, ammonites, their principle prey, became extinct during the event. Many shell-building marine animals were affected by the event, possibly due to problems in building their shells because of disruption of mineral balance in the oceans. The ammonites may have taken the mosasaurs with them. ---
**Author:** ![John\_Mace](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_mace/32/185_2.png) [@John\_Mace](https://boards.straightdope.com/u/John_Mace)\ **Post date:** [December 21, 2015, 8:42pm UTC](https://boards.straightdope.com/t/dinosaur-extinction/740940/51 "2015-12-21T20:42:52Z")
> [@Chronos](#): > > There were at least three lines of hominids who reached the point of making and using tools (things like clay and flint): Us, Neanderthals, and Floresiens. Granted that we’re all three pretty closely related, but how smart was the most recent ancestor of those three? Did the big jump happen once, from chimplike intelligence to that creature, or did it happen three times, from that creature to the three tool-users? **Chronos** : Coming back to those questions for a minute, there isn’t really an easy answer. The hominin\* tree looks bushier and bushier all the time, and at any give time there were probably several species wandering around all of whom might have been interbreeding, too. Traditionally, though, we have defined the genus Homo as “stone tool making”, so when we first found modified stone tool, the assumed too maker was called _H. habiilis_. They made simple choppers that were thought to be used to crack open bones to get at the marrow. Brain size was slightly bigger than chimp size, but still pretty close. But _H. habilis_ has been a controversial species ever since it was described and some anthropologists would lump them in with one of the Australopithecines. To complicate things, modified stone tools have been found recently that seem to be associated with Australopithecine bones (2-3MYA), so maybe they were a stone tool maker, too. Whether making those stone tools was a “big jump” or not is debatable. \*H. erectus \*(and the other associated species) really did comprise a “big jump” though, as the level of sophistication of the hand axes far exceeds that of the choppers. Just how many Erectus-like species there were is debatable, and you see all sorts of names floating around identifying local variants. But, for simplicity’s sake, it’s sometime easier to just talk about Erectus-like species. Erectus was also the first species to leave Africa (although that is somewhat in dispute), and there’s a famous fossil site dating to about 1.7MYA in [the former Soviet Republic of] Georgia. Erectus is also credited with taming fire, which is a really big jump. Brain sizes for these guys were ~ 1/2 - 2/3 of ours, and they first appear about 1.8MYA in the fossil record. The funny thing is, though, as smart as these guys were, their tool kit didn’t change much at all for over a million years, so that makes one wonder just how “smart” they were. \*Hominin is the term more commonly used there days to denote Us + our ancestor back to the time our line split from the chimp line. ---
**Author:** ![carnivorousplant](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/carnivorousplant/32/3563_2.png) [@carnivorousplant](https://boards.straightdope.com/u/carnivorousplant)\ **Post date:** [December 21, 2015, 8:55pm UTC](https://boards.straightdope.com/t/dinosaur-extinction/740940/52 "2015-12-21T20:55:55Z")
> [@John\_Mace](#): > > The funny thing is, though, as smart as these guys were, their tool kit didn’t change much at all for over a million years, so that makes one wonder just how “smart” they were. Did they need to do anything differently during that million years requiring different tools? We use different tools to work on a steam engine that a PC, but did their behavior change from cutting up dead things to eat? ---
**Author:** ![Really\_Not\_All\_That\_Bright](https://avatars.discourse-cdn.com/v4/letter/r/e8c25b/32.png) [@Really\_Not\_All\_That\_Bright](https://boards.straightdope.com/u/Really_Not_All_That_Bright)\ **Post date:** [December 21, 2015, 9:24pm UTC](https://boards.straightdope.com/t/dinosaur-extinction/740940/53 "2015-12-21T21:24:33Z")
> [@Colibri](#): > > Actually, ichthyosaurs and pliosaurid plesiosaurs were already long extinct by then, having disappeared about 25 million years earlier for unknown reasons. > > The remaining plesiosaurs and mosasaurs were large, active predators that probably fed on live prey and would have been more susceptible to disruption of the food chain than crocodiles, which can survive as scavengers. In the case of the mosasaurs, ammonites, their principle prey, became extinct during the event. Many shell-building marine animals were affected by the event, possibly due to problems in building their shells because of disruption of mineral balance in the oceans. The ammonites may have taken the mosasaurs with them. Fascinating. Thanks. ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [December 22, 2015, 12:15am UTC](https://boards.straightdope.com/t/dinosaur-extinction/740940/54 "2015-12-22T00:15:50Z")
> [@Colibri](#): > > … Even in our own lineage, the benefits of intelligence didn’t really become apparent until we reached the technological stage a few thousand years ago. We and our ancestors spent millions of years as by far the most intelligent species on the planet without it making us exceptionally successful compared animals with much less brain power. In fact, hominids have been pretty rare almost throughout their evolutionary history. > [@John\_Mace](#): > > Our ancestors were pretty successful compared to other ape species, though, since they colonized so many different climate zones not by adapting physically so much as using technology. But yeah, being a hunter/gatherer pretty much limits your total population size since you need so much more land per person to survive. If we look at other large mammalian carnivores, they tend not to be very numerous and we’d fit a similar pattern. > [@Colibri](#): > > Even after the acquisition of fire, probably by Homo erectus, allowed colonization of the temperate zone populations were still very sparse and probably often went locally extinct. But the relative lack of success of apes in general helps make my point as well. … I have no expertise in this area, but this convo about limited success of intelligence reminded me of this: [xkcd: Land Mammals](http://xkcd.com/1338/). It’s humor of course, but given the author I think we can safely assume it’s well-researched and fact-based. It seems the main beneficiary of human intelligence is … cows. They certainly outweigh us by a large margin. And given their relatively short lives as we manage them, they also certainly outnumber us over our lifetimes as well despite their 5-10x larger individual weight. Bottom line: So we’ve finally figured out what intelligence is actually good for: having cows!! 🙂 ---
**Author:** ![John\_Mace](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_mace/32/185_2.png) [@John\_Mace](https://boards.straightdope.com/u/John_Mace)\ **Post date:** [December 22, 2015, 1:34am UTC](https://boards.straightdope.com/t/dinosaur-extinction/740940/55 "2015-12-22T01:34:17Z")
> [@carnivorousplant](#): > > Did they need to do anything differently during that million years requiring different tools? The ones that didn’t do anything differently aren’t around anymore. So I guess you could say the didn’t “need” to do anything different as long as they were OK with going extinct sooner than those who did do things differently (us, and those who became us). ---
**Author:** ![carnivorousplant](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/carnivorousplant/32/3563_2.png) [@carnivorousplant](https://boards.straightdope.com/u/carnivorousplant)\ **Post date:** [December 22, 2015, 3:36am UTC](https://boards.straightdope.com/t/dinosaur-extinction/740940/56 "2015-12-22T03:36:53Z")
> [@John\_Mace](#): > > The ones that didn’t do anything differently aren’t around anymore. So I guess you could say the didn’t “need” to do anything different as long as they were OK with going extinct sooner than those who did do things differently (us, and those who became us). What species did what things differently during those millions of years? ---
**Author:** ![John\_Mace](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_mace/32/185_2.png) [@John\_Mace](https://boards.straightdope.com/u/John_Mace)\ **Post date:** [December 22, 2015, 3:43am UTC](https://boards.straightdope.com/t/dinosaur-extinction/740940/57 "2015-12-22T03:43:01Z")
> [@carnivorousplant](#): > > What species did what things differently during those millions of years? You asked if _H. erectus_ “needed” to change. The answer can only be seen in hindsight. Those populations of Erectus that didn’t change are no longer with us. Certain of those populations that did change became us. ---
**Author:** ![Urbanredneck](https://avatars.discourse-cdn.com/v4/letter/u/ea5d25/32.png) [@Urbanredneck](https://boards.straightdope.com/u/Urbanredneck)\ **Post date:** [December 22, 2015, 6:12am UTC](https://boards.straightdope.com/t/dinosaur-extinction/740940/58 "2015-12-22T06:12:33Z")
Still surprising that with all the competition, an intelligent species of dinosaurs didnt develop in all those millions of years. We already know many dinos lived in large family groups or packs and probably worked together for protection and/or hunting. So if a species has opposable thumbs, a language, and works as a group why dont they develop? Look at the intelligent behaviors of many insects such as bees and ants. ---
**Author:** ![John\_Mace](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_mace/32/185_2.png) [@John\_Mace](https://boards.straightdope.com/u/John_Mace)\ **Post date:** [December 22, 2015, 6:32am UTC](https://boards.straightdope.com/t/dinosaur-extinction/740940/59 "2015-12-22T06:32:55Z")
Corvids and Parrots, all dinosaurs, are some of the most intelligent animals on the planet. ---
**Author:** ![MrDibble](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mrdibble/32/114_2.png) [@MrDibble](https://boards.straightdope.com/u/MrDibble)\ **Post date:** [December 22, 2015, 7:27am UTC](https://boards.straightdope.com/t/dinosaur-extinction/740940/60 "2015-12-22T07:27:36Z")
> [@John\_Mace](#): > > Corvids and Parrots, all dinosaurs, are some of the most intelligent animals on the planet. [Tool-users and tool-_ **manufacturers** _](https://en.wikipedia.org/wiki/New_Caledonian_crow#Tool_use_and_manufacture), even. [Previous page](https://boards.straightdope.com/t/dinosaur-extinction/740940.md?page=2) [Next page](https://boards.straightdope.com/t/dinosaur-extinction/740940.md?page=4)