# Why were dinosaurs so big? **URL:** \ **Category:** Cecil's Columns/Staff Reports\ **Created:** [September 6, 2013, 3:08pm UTC](https://boards.straightdope.com/t/why-were-dinosaurs-so-big/668178 "2013-09-06T15:08:20Z")\ **Posts on this page:** 6\ **Page:** 2
**Author:** ![RedSwinglineOne](https://avatars.discourse-cdn.com/v4/letter/r/a9adbd/32.png) [@RedSwinglineOne](https://boards.straightdope.com/u/RedSwinglineOne)\ **Post date:** [September 20, 2013, 10:42pm UTC](https://boards.straightdope.com/t/why-were-dinosaurs-so-big/668178/21 "2013-09-20T22:42:12Z")
> [@Coccinelle](#): > > That is to say that if you double in size, your energy demands will be less than double… I’m not sure if this is true, but even if we assume that it is… > [@Coccinelle](#): > > This would give a clear evolutionary advantage to getting big, should time and circumstances be in your favour. …this does not necessarily follow. Even if your energy demands only increase by 50%, that’s still 50% more energy required to live. Unless being larger provides some benefit (like making a new food source possible), it would still be a disadvantage to be larger. ---
**Author:** ![dropzone](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dropzone/32/7515_2.png) [@dropzone](https://boards.straightdope.com/u/dropzone)\ **Post date:** [September 20, 2013, 11:11pm UTC](https://boards.straightdope.com/t/why-were-dinosaurs-so-big/668178/22 "2013-09-20T23:11:28Z")
Silly humans! Everybody knows that dinosaurs aren’t ALL big. They are thin at one end, much, much thicker in the middle, and then thin again at the far end. Just big in the middle. ---
**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:** [September 20, 2013, 11:53pm UTC](https://boards.straightdope.com/t/why-were-dinosaurs-so-big/668178/23 "2013-09-20T23:53:51Z")
[A relevant paper](http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0051925). ---
**Author:** ![RiverRunner](https://avatars.discourse-cdn.com/v4/letter/r/977dab/32.png) [@RiverRunner](https://boards.straightdope.com/u/RiverRunner)\ **Post date:** [September 23, 2013, 4:59pm UTC](https://boards.straightdope.com/t/why-were-dinosaurs-so-big/668178/24 "2013-09-23T16:59:32Z")
> [@dropzone](#): > > Silly humans! Everybody knows that dinosaurs aren’t ALL big. They are thin at one end, much, much thicker in the middle, and then thin again at the far end. Just big in the middle. Is that your theory which is yours? ---
**Author:** ![Coccinelle](https://avatars.discourse-cdn.com/v4/letter/c/5f8ce5/32.png) [@Coccinelle](https://boards.straightdope.com/u/Coccinelle)\ **Post date:** [October 7, 2013, 8:13am UTC](https://boards.straightdope.com/t/why-were-dinosaurs-so-big/668178/25 "2013-10-07T08:13:40Z")
> [@RedSwinglineOne](#): > > I’m not sure if this is true, but even if we assume that it is… > …this does not necessarily follow. > > Even if your energy demands only increase by 50%, that’s still 50% more energy required to live. Unless being larger provides some benefit (like making a new food source possible), it would still be a disadvantage to be larger. That’s a very good point RedSwingLine. You’re saying it’s not clearly evolutionarily advantageous to be big for the individual animal. Well, here’s my logic, if it makes any sense. The individual animal is a unit of natural selection, but there are smaller units. The gene, for example, is perhaps the smallest unit. The gene protects itself (in a manner of speaking) in the cell, which I think can be described as another unit of selection. It is at this level that clustering together in single organisms (the individual animal) seems to be of an advantage, because together in greater numbers they conserve energy. There must be a great number of factors involved, but I propose that herbivors will grow large because there’s less caloric value in a vegetarian diet (really NOT sure that’s true) and therefor conservation of energy on the celular level is a priority. Carnivores don’tgetas big as herbivores because of the need for speed etc. Like I said though, there must be somany factors… ---
**Author:** ![huck999](https://avatars.discourse-cdn.com/v4/letter/h/d78d45/32.png) [@huck999](https://boards.straightdope.com/u/huck999)\ **Post date:** [October 7, 2013, 2:22pm UTC](https://boards.straightdope.com/t/why-were-dinosaurs-so-big/668178/26 "2013-10-07T14:22:32Z")
I Think you have all got it wrong - the definitve answer is in the book “_ **End of an Era** _” by **Robert J Sawyer**. He has obviously researched it extremely well and his conclusions are impecable ! (he says with tongue in cheek) [Previous page](https://boards.straightdope.com/t/why-were-dinosaurs-so-big/668178.md?page=1)