Why Whales Got So Big

https://www.theatlantic.com/science/archive/2018/04/why-whales-got-so-big/557213/?single_page=true

by ALee • 8 years ago

144 42 8 years ago

fouc• 8 years ago

the need to stay warm sets a floor for the body size of oceanic mammals, while the need to eat sets a ceiling. And the gap between them, Gearty found, is surprisingly narrow—and far more so than on land.

Interesting. If the range is so narrow for mammals, how did Dinosaurs get big?

ggg9990• 8 years ago

Reptiles need much less food than mammals.

bryanlarsen• 8 years ago

But birds need more food than mammals. And birds are a group of dinosaurs. Under some classification systems dinosaurs (including birds) are in the reptile tree, but in others they aren't.

AndrewOMartin• 8 years ago

Many reasons, but one reason cited for huge dragonfly-like creatures was the richer oxygen content of the air, allowing more primitive lung-like systems to support larger bodies.

fulafel• 8 years ago

Seems dinosaurs were somewhere between cold-blooded and warm-blooded, I guess they need less food for a given size compared to mammals.

MarkMc• 8 years ago

Not just less food - they produced less heat. A mammal the size of a dinosaur would not have enough surface area to get rid of the internally-produced heat.

spacehome• 8 years ago

The variable he's not talking about in that equation is body temperature. If you cut the difference between body temp and ambient temp, you proportionally cut energy needed to maintain that difference. I wonder what fundamental physiological force is keeping these mammals from evolving a lower body temperature ...

donmatito• 8 years ago

Isn't it the temperature needed for enzymes to properly work their metabolic magic (1) temperature helps reaction rates 2) enzymes need a certain temperature to maintain their shapes)

osrec2• 8 years ago

Dinosaurs were not mammals. The jury is still out on whether they were warm blooded (but most people agree that not quite as warm-blooded as mammals). The upper limit on size (according to the article) is defined by food availability and energy consumption, so I would guess food was simply more plentiful, or their energy demands were lower (due to lower core temperature). Thus they grew bigger.

TheOtherHobbes• 8 years ago

Also, average ambient temperatures in the Jurassic were significantly higher than today - up to 8C warmer according to some estimates, and even higher in the Cretaceous.

Warm blood was less of a requirement for dinosaurs than it would be today.

I don't understand how mammalian evolution worked through this period. Temperatures rose even further after the KT crash, so there would be no evolutionary benefit to being warm blooded. And yet - here we are.

masklinn3• 8 years ago

1. The snippet you're quoting is about marine mammals

2. Dinosaurs were not aquatic

3. The biggest aquatic reptiles were much smaller than modern whales (plesiosaurs and ichthyosaurs topped up around 15m long and 2 tons, which is 2x the length but 1/3rd the weight of a male Orca and nowhere near large whale league)

4. Dinosaurs weren't necessarily homeotherms and may have thus had a larger (but lower) range of efficiency

5. As the snippet notes the upper bound has to do with food limitations, and large sauropods largely evolved ways to mow down ridiculous surfaces (and thus amounts of food), which could have combined with higher plant growth/density from higher O2 levels to put a higher cap on food issues

pfarnsworth• 8 years ago

Your point of #3 is probably wrong. It’s harder to get fossils of aquatic creatures so there’s likely a vast number of animals that we will never know about. Saying with certainty that the biggest aquatic reptiles were smaller than whales is a logical fallacy. Only the ones we know about are smaller but we don’t know if there ever were, we might get lucky and find a fossil that is larger.

todd8• 8 years ago

Looks like there is a small typo: should read “higher in CO2” whouldnt that produce faster plant growth?

Avshalom• 8 years ago

While it's obviously not a hard and fast law and I have gotten into arguments with people way above my pay grade over that:

https://en.wikipedia.org/wiki/Cope%27s_rule

not as an explanation of why whales are big, just a sort of interesting bit of related history.

mirceal• 8 years ago

Know it’s an expression, but not sure how pay grade factors into an argument like this.

brianwawok• 8 years ago

"Above one's pay grade" is a colloquialism

https://www.merriam-webster.com/dictionary/colloquialism

tw04• 8 years ago

It's borderline, but still makes perfect sense. In academia, more seasoned professors generally fall into a higher pay grade. Hence he's argued with people that in theory have more experience than he (or she).

dang• 8 years ago

We detached this subthread from https://news.ycombinator.com/item?id=16780429 and marked it off-topic.

cparsons3000• 8 years ago

So will humans continue to get bigger if we don't hit a world wide food constraint?

fahd777• 8 years ago

Did you read the article in its entirety? :)

aalleavitch• 8 years ago

This article made me imagine mouse-sized dolphins, and now I am sad they do not exist.

mkempe• 8 years ago

Imagine having a flock of kitten-sized giraffes roaming about your house and gently grazing on your plants.

hexane3602• 8 years ago

And they evolved a foraging technique called lunge feeding, where they accelerate into a shoal of prey, open their ballooning mouths, and suck in vast volumes of water.

This is terrifying.

kneel• 8 years ago

I wonder if this could be related to the size of pacific islanders. I remember reading somewhere that is was somewhat of a paradox how people living on small islands for so long became so large.

People from the pacific have been long been adept fisherman using techniques such as deep diving spearfishing.

Pacific islanders are also enormous. They're overrepresented in the NFL for a good reason. Anyone who has ever met a family of Samoans knows that these people have very different genes.

Baeocystin• 8 years ago

Such changes based on the unique environmental pressures of species living on islands comes under the heading of Foster's Rule:

https://en.wikipedia.org/wiki/Foster%27s_rule

Interestingly, species will both grow or shrink, depending on their initial niche before becoming an island population, as well as local resource availability.

danieltillett• 8 years ago

Have a look at what the ancestors of the current Pacific Islanders were doing for a few thousand years. They lived in an environment where growing food is easy and starvation almost unknown, contagious disease minimal, yet the population static. Which of the four horsemen was responsible?

craftyguy• 8 years ago

I've heard a different explanation (from Jared Diamond): it's because of the introduction and proliferation of high calorie, cheap foods. You see this in many 3rd world countries (e.g. central/south America, many poor towns in the US, etc) that have easy access to type of food.

nikofeyn• 8 years ago

interesting article, but there’s a small mistake. i don’t think it’s accurate to say that sea otters spend a lot of time on land. i think it’s actually fairly rare for them to go on land.

Why Whales Got So Big

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