Doctor Who sent me down a rabbit hole and you have to come with me

So I guess this is how I usher in the new era of the No-Brainer on Buttondown [ed. note on 5/14/24: now Beehiiv, lol]. Sorry for any glitches, especially with the footnotes! I still haven't quite figured those out—growing pains and all that.

Anyway, like many people who somehow survived pop culture in the 2010s, I've been pretty excited for the new season of Doctor Who coming up. So the new trailer should have been a good thing, but unfortunately, it's sent me on an hours-long tale of woe.

The trailer shows the titular time traveling maestro Doctor and his friend, Ruby Sunday (great name), looking over a field of dinosaurs, where Ruby asks what would happen if she stepped on a butterfly—as in, would it royally fuck up the future. (Y'know, like the butterfly effect.) Of course, she immediately proceeds to step on a butterfly:

This is clearly nonsense. There were no immediately obvious monarch butterflies in the time of the dinosaurs, right? So I made a joke about it to a friend and moved on.

Well, I should have moved on. But I had essentially made a promise that I would be pedantic, and here at No-Brainer Industries, we honor dubiously extant promises. On top of that, a question kept nagging at me: how wrong is it?

Butterfly fossils, turns out, are difficult to find. Bugs are a lot more delicate than something bony like a reptile or mammal. The Natural History Museum in the UK has one that looks a lot like a modern-day butterfly that's 34 million years old, which would put it after the time of the dinosaurs (the meteor smacked the dinosaurs around 65 million years ago).

Lucky for Who, that's actually not the oldest lepidopteran (the group that includes moths and butterflies, stay tuned for more taxonomy!) fossil. That honor belongs to a 200 million-year-old specimen found in pond scum, which would put the earliest butterflies and moths right at the beginning of the Jurassic period.  Or, put simply, butterflies and moths did coexist with the dinosaurs.

But while Who is coming out ahead for now, we're not done yet. Those old-ass bugs probably looked like this, not an instantly recognizable "monarch butterfly." ¹ So when did monarch butterflies specifically evolve?

A common number I saw a lot was about 2 million years ago, which would be a major L for Who. (It's also the kind of hundreds-of-millions-of-years mistake that I was expecting.) However, I had a difficult time finding a legitimate citation,² which cast that number into doubt. I finally turned to Wikipedia out of frustration, and thankfully, it turns out Wikipedia is pretty good at citing sources from legit science journals³ . Unthankfully, that "2 million" number isn't quite what we're looking for. People think that the North American and South American variants of the genus that includes monarch butterflies (danaus) diverged around that time, not necessarily that monarch butterflies emerged as a species then. So we're still not done yet.

Believe it or not, the trailer doesn't give a clever footer specifying what kind of danaus species we're dealing with here. We don't even know where on Earth they are in those screencaps, which rules out using geography to narrow down possible candidates in danus. I could try to just eyeball what kind of danaus butterfly the screencap is showing, but I'm no entomologist, and a lot of them look pretty similar without a geographic area to jump off of.

But instead of corralling a list of similar looking danaus butterflies and trying to find when each of them evolved, a route I DEFINITELY didn't waste precious time in one life on, I'm going to take a shortcut. We're working on a scale of millions of years, so instead of working species by species, I'm going to go up two levels of taxonomy. Species (like the North American monarch butterfly) are the most specific group in the extremely boring science that is taxonomy; a genus (like danaus) is one step up from that and includes multiple species; and in this case, the sub-tribe dainini includes multiple genuses of butterflies related to monarchs. So we're losing the specificity of "this exact butterfly evolved around this many years ago," but it's a lot faster to find out when dainini evolved.⁴

Like everything about this post, it turned out to be more difficult than I thought to pin this down, but the best I can do (it's 2:30 AM) is this paper that says one of the oldest butterflies in this group was likely flapping around in the mid-oligocene period... which ended 23 million years ago. I can't find an image of what it may have looked like, but even if I want to give this situation the biggest benefit of the doubt I can and assume this predecessor somehow looked a LOT like a modern day monarch butterfly, we're still... how many years off again?

Ah right. I didn't even pin down when in time the Doctor and Ruby actually are in this screencap, did I. Look, I'm so tired, and that big long neck thing sure looks like a brontosaurus⁵ from far away, so I'm just not going to interrogate that any more. Brontosaurus lived during the late Jurassic and early Cretaceous periods, which would be about 100.5 million years ago. So Doctor Who is off by about 77.5 million years. Mystery solved and good fucking night!

1  Fun fact: this fossil suggests that butterflies and their proboscis-sporting ilk actually precede the flowers we thought they fed on—those were supposed to crop up 130 million years ago.

2  You'd think the World Wildlife Fund would be better at citing sources, but I get it. They're busy with the plushies! Did anyone else DESPERATELY want one as a kid?

3  But you still need to check those sources!

4  Evolutionary lines tend to get more specific as a function of time: we all started as single cells, then there was a difference between single cell and multicell organisms, then what kind of multicell organism... so on and so forth. So to avoid doing a fuckton more entomology research, I'm going to treat the entire subtribe of dainini butterflies as the end of the evolutionary line for our purposes.

5  I saw for a second that "brontosaurus" might not be a real kind of dinosaur, which I swear to god almost broke me, but a bunch of nerds decided in 2015 that there was enough evidence to reinstate it with its dino pals.