Friday, 7 April 2017

Parasites Bug Creationists

Several specimens such as this Cimex latipennis female found in the Paisley Caves in Oregon date nearly 11,000 years ago.
Photo credit: Martin E. Adams
Cimicid Remains Found in Oregon Caves are Oldest Ever Found – Entomology Today

Newly discovered bat-bugs from the floor of a cave in Oregon are the earliest so far found - and it's bad news for creationists, again.

Parasites are a problem for creationists for number of reasons and not just that so many creationists are susceptible to parasitic frauds who sell them spurious confirmation of their superstition for large amounts of money. It's no accident that so many creationist charlatans are multi-millionaires while the people they live off are amongst the poorest of people.

Parasites are a problem because they show close parallel evolution with their hosts, often expressed as an arms race, belying any notion of intelligence in evolution, but also showing an amazingly close mapping of their own diversification over time with that of their hosts' diversification. For example, the diversification of the species-specific lice which live on the African apes and on humans can be mapped precisely onto the diversification of Homo, gorilla, chimpanzee and bonobo showing that the different species of lice are as closely related to one another as humans and the other African apes are to one another.

But there is one group of parasites that map a more recent development in human evolution that occurred around about the time that we branched off the hominin line and adopted a more settled existence relying on permanent or at least semi-permanent shelters, often caves, as the base for small hunter-gatherer clans. This life-style was maintained as humans spread out of Africa into Eurasia and eventually the New World. This created a new opportunity for a new set of parasites and fellow travellers to exploit - cockroaches, house mice, house sparrows, and, the case in point, bed bugs.

Bed bugs, Cimex lectularius and Cimex hemipterus, are entirely dependent on humans and the houses in which we live. They do not exist in the wild. They are, however, very closely related to bat bugs that live in caves where bats roost and on which they prey. It is believed that the bat bugs of Africa and Eurasia adapted to parasitise the new occupants of these caves - humans.

But it seems that not all bat bugs were able to make that transition, particularly in the New World, for reasons which are not understood. It maybe that either the population of bugs or the population of humans were too small to establish genetically isolated populations or maybe they simply couldn't make the necessary transition.

A paper published a few days ago in the Journal of Medical Entomology reports on fourteen examples of what are believed to be the earliest examples of the Cimex order, placing them from between 5,100 and 11,000 years old with thirteen of the fourteen between 9,00 and 11,000 years old. This if of course a probl em for any creationist stuck with trying to believe Earth is just 5,000 years old. Facts, however rarely inform creationist belief, so they should be able to wave them aside as unimportant.

The specimens were found in the Paisley Five Mile Point Caves, Oregon, USA. These caves have an interesting geological history that makes dating objects found in the floor sediment especially easy The caves were formed by wave action on the shore of Lake Chewaucan. The level of this lake fell near the peak of the last Ice Age, between 18,000 and 19,000 years ago, leaving the floor exposed and consisting of sandy gravel between wave-rounded boulders and pebbles. So, this represents the base of the geological column with a fairly precise known date. Everything above has been deposited since and represents a record of changes in the cave's ecology.

The basal layer is low in organic content and is overlain by a gravelly, organically rich layer containing twigs and mammal bones forming 15 well-ordered strata which have been carbon dated to between 12,425 and 11,560 years ago. Over this is a layer of water-lain silt from a brief inundation believed to be due to a single intense storm about 10,980 years ago. This silt acts as a seal on the strata below it.

Were the cimicid populations too small to establish themselves outside the caves, or were the host populations too small? Given that Paisley Caves was only a seasonal occupation area for human hunter-gatherers, did the humans move around too much, or were the bugs not able to withstand the environment outside the caves for very long? Or, were there other constraints involved? I’m working on these last few archaeological questions right now.

Martin E. Adams,
Paleoinsect Research. Co-author.
On top of this silt layer is an organically-rich, highly compacted layer consisting almost entirely of bat guano mixed with wood rat faeces and nesting materials, pronghorn hair, bones, fur, feathers, faeces, and other organic material. This layer records when bats first occupied this cave and it is in this layer that almost all the Cimex specimens were found.

This layer is then overlain by wind-blown Mount Mazama tephra deposited roughly at 7,640. Carbon dating has shown that the bat guano layer accumulated at a mean rate of about 1 cm every 60 years.

The interesting thing for the story of the evolution of humans and their parasites is that this cave is also the site of some of the earliest evidence oh human activity in the New World and yet the modern bed bugs which are so well established in North America and especially in New York hotels is not descended from these bat bugs but from the same bat bugs as in the rest of the world. The earliest known ancestor of those bugs was found in Egypt, dated from about 3,500 years ago.

Of course, as mentioned earlier, these newly-discovered, accurately-dated bat bugs of the Cimex genus represent a problem for creationism because they inconveniently predate Earth, as does the evidence of human occupation of this cave, if one subscribes to the evidence-free Young Earth Creationist dogma.

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