High up on the list of ecologically invasive mammals are the cat, the rat and the house mouse. At least the felines grew on us, but the rodents are another story. Now a vast international team has cast its scientific searchlight on the burning question of where the house mouse came from anyway, when, how it spread, and why.
“The house mouse (Mus musculus) represents the extreme of globalization of invasive mammals,” write Thomas Cucchi from the Natural History Museum in Paris and colleagues – rather unkindly considering that if anything, Homo sapiens is the ultimate extreme of invasive mammals. We sapiens reacted to the rodent invasion by first tolerating, then encouraging an invasive proxy predator that can kill micro-mammals very efficiently, if it’s in the mood.
The new study by Cucchi and the team is based on the cutting-edge analysis of 829 dental remains from house mice, extracted from 43 archaeological contexts in Southwestern Asia and Southeastern Europe. The oldest mouse was 40,000 years old and the youngest, 3,000 years old, as the team reported Tuesday in Nature Scientific Reports.
And the outcome: The house mouse joined our house in the Levant in the early Neolithic era, when Natufian hunter-gatherers became sedentary about 14,500 years ago, the scientists deduced. By 12,000 years ago they were farming and storing grain in the Levant; and as farming spread, so did the mice. And, it turns out, the cats.
Out of Indo-Pakistan
Geographically speaking the house mouse technically originated in the vicinity of the Indo-Pakistan subcontinent, Iran and Afghanistan, and spread to the Mesopotamian area during the Pleistocene, a period dating from about 2.5 million years ago to 11,700 years ago. The little creatures only seem to have arrived in the southern Levant 14,500 years ago, and the northern Levant 12,000 years ago.
To be clear, micro-mammals throng the planet but we are talking specifically of the house mouse, Mus musculus. During the Pleistocene the stem Mus evolved into three main Mus musculus subspecies, all of which moved in with humankind, becoming one of the most successful commensals of all time, the team wrote — referring to animals that attach themselves to humans, without any advantages to the people but without harming them either.
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But it was only in the Levant where people began to form sedentary patterns, then farm that Mus embarked on its commensal relationship with us (which means they stole grain without the humans much noticing).
The transition from a life of nomadic hunting and gathering to a sedentary life of growing crops, augmented by sporadic hunting and gathering, was a slow, stuttering process that seems to have developed independently in different places during the Holocene, as the Ice Age wound down and global temperatures rose. There is evidence that agriculture developed independently in New Guinea, for instance.
In our part of the world, farming may have begun in Turkey, Iran and Israel, and would only reach Europe thousands of years later. As the innovation of farming crept through the Near East over thousands of years, so did said mice, keeping pace with the adoption of agriculture. From there, “stowaway transport of house mice to Cyprus can be inferred as early as 10,800 years ago,” the authors write.
The conquest of mainland Europe by the house mouse did not happen until the Europeans belatedly began to settle down and to grow and trade food, starting about 6,500 years ago in Eastern Europe and 4,000 years ago in Southern Europe, the team notes.
Meanwhile, throughout the process, as the mouse joined the house, so did the cat. By the time this whole dynamic reached Europe in the Late Neolithic or early Chalcolithic periods, our relationship with cats had evidently passed beyond the commensal: its exploitation of our rodent-infested granaries – and became willing on our part.
The researchers suggest that the dispersal of cats in Europe was actually “human mediated”: They were deliberately brought over from Anatolia. The cat reached current Bulgaria by 6,400 years ago, Romania by 5,200 years ago and Poland by 5,000 years ago.
I tink I saw a giant puddy tat
The Homo genus has been spreading since we had legs, it seems. Whether because of innate wanderlust, curiosity, competition, crowding in the cave or whatever – hominins began leaving Africa about two million years ago. The oldest-known skeletons outside Africa associated with our line are a collection of small-brained Homo erectuses found in Dmanisi, Georgia, dating to 1.8 million years ago.
The more or less constant seep of hominins from Africa culminated, as far as we are concerned, with the exit by the ancestral, modern Homo sapiens about 50,000 years ago. These early modern humans – and their cousins in Europe, the Neanderthals and Denisovans – were not farming: They were hunting and gathering. They didn’t have a rodent problem; they had a big-cat and wolf problem.
The Neolithic transition from being hunter-gatherers to farmers was extremely gradual. Some evidence in Israel indicates early stabs at grain cultivation as early as 23,000 years ago. Some think the very first farmers in the region were in today’s Turkey. But be that as it may, remarkably, archaeologists identified the known earliest bread, an unleavened loaf, from 14,400 years ago in Jordan. And there you have it: That’s when the mouse took up house in our region and in its wake, the cat.
Technically, the team identified the remains as mice by their teeth, radio-carbon dated the remains, and analyzed their mitochondrial DNA.
One caveat to the research is that further study could find earlier evidence of human—mouse cohabitation; maybe they plagued the mud-and-reed homes of earlier folk as well. But the conclusion that the mouse entered into its commensal relationship with us in the Levant 14,500 years ago is based on current evidence.
There is a lesson for the ages in this story. Life has come and gone and spread and died out since the beginning of time. But biological invasions have drastically increased with human activity, the team stresses. “The house mouse is emblematic of these anthropogenic biological invasions threatening biodiversity,” they write.
People obsess over the rat, which also spread around the world in our luggage, but these researchers deem the “elusive” house mouse a much more successful biological invader – almost as successful as we are. And thus the humble mouse, which non-farmers among us tend to regard with affection, in contrast to our “friend” the rat, is an indicator of the human impact on biodiversity, which is great and terrible.
As for the cat, a study of mitochondrial DNA suggests that the African wild cat (Felis silvestris lybica) was “domesticated” amid the rise of agriculture in the Neolithic Near East.
The earliest archaeological evidence of cats in Europe dates to around 3,000 years ago – again, about 1,000 years after the advent of sedentary life and farming there – and following the invasion of the house mouse.
Early farmers in Southeast Asian also had a problem with rodents eating their millet, and they solved it similarly. Archaeologists have identified millet isotope signals in rodent skeletons from the Asian Neolithic – and in those of the cats that ate the rodents. But we don’t have specific information about the spread of the local mice subspecies in southeast Asia, Thomas Cucchi tells Haaretz: remains of small vertebrates have not been extensively collected in archaeological sites in this area.
By the way, if there were early worshipers of the cat, maybe they were in Cyprus. The cat was clearly a household member on the island as long as 11,000 years ago, which was 5,000 years before the earliest evidence of cat domestication in Egypt. A cat was buried with a woman in on Cyprus 9,500 years ago, predating Egyptian cat art by 4,000 years. The cats had to have been brought there by boat, on purpose, as the island is 70 kilometers off the Turkish coast.