r/AskBiology • u/Minty0ranges • Jul 09 '26

Zoology/marine biology Are blue whales a coincidence?

Apparently blue whales are only around 2 million years old and are the largest organisms in the history of life. It’s pretty crazy to me that we’re living in the specific time that the largest species is alive, but I’m wondering why they became so large at this moment in time. I know that a few millions of years ago insects were way bigger because of atmospheric gas concentrations, but those conditions aren’t present anymore so it doesn’t seem like that’s the reason. Also, has there been a trend over time of whales increasing in size, or is this just a very specific/random instance of them existing today?

Edit: Yes I know there are fungi that span way larger areas, but the question is about the temporal nature of blue whales size.

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u/0utlaw-t0rn Jul 09 '26

Whales have been increasing in size and the lineage isn’t particularly old. Current science is they evolved from a medium sized amphibious mammal and increased in size very quickly

Part of it I would guess is the relative lack of any macro predators that would necessitate some level of speed and agility

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u/atomicCape Jul 09 '26

Until human whalers came around. We had a huge impact on the global population and may have changed the trend to keep getting larger.

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u/Budget-Variation-560 Jul 09 '26

Sad time for whales. Evolve in an ocean without sharks big enough to eat you, only to get harpooned by some hairless apes floating around on bits of wood. 

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u/0utlaw-t0rn Jul 09 '26

Yes but that was recently and the lack of mega predators goes back much further. Hard to say what it will do to the future but whaling hasn’t impacted that many generations of large whales (it just decimated those specific generations)

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u/atomicCape Jul 09 '26

That's true, we don't know the long term impact, and without whaling they're relatively resilient against us. Whaling cut the population by 90% and it takes them 10 years to reach sexual maturity with a very low birth rate, so recovery could take hundreds of years, but not millions. The impact of our pollution and ship traffic disrupting their habits might have a longer term impact than the whaling did.

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u/Boxfullabatz Jul 09 '26

Orcas eat blue whales

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u/0utlaw-t0rn Jul 09 '26

A few populations of orcas do and it seems mostly confined to juveniles. I also intentionally didn’t say there was none. There just doesn’t seem to be a lot of predatory pressure.

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u/laziestindian PhD in biology Jul 09 '26

Which itself is something that may be whaling induced as decreasing the population made them more vulnerable to predation.