The Origin Of Cockroaches Can Be Traced Back To The World’s Last Supercontinent

Pangaea, everyone’s favorite – but not the first – supercontinent, was a jigsaw in motion, carrying and dispersing all kinds of life. Completely coming together as one single ginormous piece around 270 million years ago, it broke up again just 70 million years later. In the process, it brought countless biological communities together before casting them asunder again.

One international team, led by the University of Sydney and the Okinawa Institute of Science and Technology, has now found out that the gigantic landmass played a role in the evolution of everyone’s least favorite creepy-crawly too: the cockroach.

The first fossils that can be properly attributed to contemporary cockroaches can be found in the Cretaceous Period, around 140 million years ago. This record has suggested to researchers that their lineage of living cockroaches dates back around 200 million years ago, during the supercontinent’s disintegration, but the details here remained somewhat unclear.

This team’s new work, published in the journal Molecular Biology and Evolution, has significantly revised their scuttle-heavy history.

They looked at the complete mitochondrial genomes of 119 living cockroach species, as well as a handful of termites, mantises, and other related groups, and found that their last common ancestor lived 235 million years ago before Pangaea began to properly break apart.

Mitochondrial genomes aren’t the same as your nuclear DNA. They’re separate genetic coding instructions found within the powerhouses of cells, which are only passed down maternally. Left pretty much unaltered and unmutated, unlike their nuclear cousins, they are rather useful to geneticists that are trying to trace family trees back through time.

By looking for specific genetic markers and comparing and contrasting these with others, common ancestors can be found, as if triangulating on a map. That’s essentially how this enigmatic 235-million-year-old ancient ancestor – not the original cockroach, mind you, but a progenitor of them – was identified.

Cockroaches, as noted by the official press release, aren’t great fliers. They probably didn’t tend to fly across the ocean from landmass to landmass as their once whole supercontinent began to shatter. Today, their distribution is almost global, with only the highest latitudes experiencing a dearth of cockroachian crusaders.

The team notes that this revised timing means cockroach ancestors drifted on the fragments of Pangaea as they made their way across and around the world. By reconstructing the geographic ranges of these ancestral beasties, they found “tentative support” that there was indeed vicariance – geographical segregation – “within and between several major lineages”.

This means that the destructive action of plate tectonics tore families and some closely related families apart, and these little monsters just went with it, evolving into new species, extinct and extant, along the way.

In some cases, particularly across the Australian, Indo-Malayan, African and Madagascan regions, the team’s genomic work suggests that there was transoceanic dispersal too – meaning cockroaches snuck across in tiny, vegetation-based rafts, or perhaps were washed across small inlets by the tide.

Either way, they’re now everywhere, much to everyone’s chagrin. They’re generally considered to be pests, those that spread disease and leave funny smelling unguents behind. However, in certain parts of certain countries, cockroaches are considered to be a nutritious food source. Each to their own, we suppose.

Either way, it’s safe to say that they’re incredibly hardy. Not only is it likely that they could survive the aftermath of a nuclear war, but their lineage survived the destruction of a supercontinent. Fair play, you nasty little demons.

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