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05/02/2016
Evolution- Sexy and Otherwise
CHAPTER 68 Evolution, Forward and Back
Sex sells. At least that's what one concludes from the content of many popular movies, TV shows and other media. So, let's begin with evolutionary sex and a report by Ann Gibbons titled "Five matings for moderns, Neandertals" in the March 18 issue of Science. In previous columns, I've discussed findings that those of us of European ancestry have inherited a few percent of our DNA from intimate contact between our out-of-Africa modern human (homo sapiens) ancestors and Neandertals. Gibbons cites a report by an international team published online in Science that reveals " a far richer sexual past for modern humans and their archaic cousins." The researchers have used powerful new statistical approaches to determine how often Neandertals and another brand of archaic humans known as the Denisovans mated with us moderns and also with each other. Combining the recent studies with earlier DNA fossil data, our modern human ancestors and Neandertals mated at least five times.
Researchers have really been busy tracking down the liaisons between the various groups.
For example, they found that a 40,000-year-old modern human from what is now Romania had a great-great-great grandparent who was a Neandertal. On the other hand, a toe bone of a Neandertal had some modern DNA in it, suggesting the possibility that we moderns were involved in hanky panky with Neandertals 100,000 years ago. But the Neandertals and the Denisovans apparently were getting together over 400,000 years ago. These two groups of non moderns seem to have mixed it up so often that sometimes scientists have trouble telling the difference between Denisovan and Neandertal DNA. For Africans, no problem. They stayed at home and their DNA has no contributions from either Denisovans or Neandertals.
So much for sex. Let's turn to another, less glamorous evolutionary topic - pooping, more specifically, what Amy Maxmen terms "one of the finest innovations in the past 540 million years of animal evolution", the butthole. Maxmen discusses the anus and its evolution in an article titled "Comb jelly 'anus' guts ideas on origin of through-gut" in the March 25 issue of Science. It seems that the first animals that appeared on Earth did not have this bodily feature and hence had to eat their food and expel the resulting waste through their mouths. Today, some of the descendants of these early creatures, such as jellyfish, sea anemones and sea sponges, still eat and excrete through the same opening. Once some animal or animals evolved another opening for excretion of waste, the variety of animals took off and we have the huge variety of animals living today, not to mention animals such as the dinosaurs that have gone extinct. Maxmen suggests that the development of the anus lifted restrictions on the length of animals, noting that having a butthole allowed an animal to both eat and digest food at the same time. Without the two openings, we would have to excrete before we eat again.
Actually, the main point of the article was the result of a revolutionary study on a comb jelly by William Browne at the University of Miami. The comb jelly is translucent and you can watch the critter eat its food. Decades ago, workers had watched the comb jelly eating food and then excreting it through the same opening. What Browne did was to engineer some small crustaceans and zebrafish to glow red with a fluorescent protein. When eaten by the comb jelly, the flow of them through the comb jelly's translucent body could be observed clearly. After the jellies had eaten Browne monitored them with a video setup for 2 to 3 hours and was shocked to see the food exiting the jelly from pores in the other end. When he showed the video at a meeting the attendees were just as shocked. Speculation is that perhaps the earlier studies involved either overfeeding or feeding unpalatable food to the jellies and that researchers back then were seeing vomiting. Browne also saw hints of sphincter muscles around the pores in the comb jellies. The finding of the exit in the comb jelly has evolutionary significance inasmuch as the comb jelly is believed to have evolved earlier than other animals having just one hole. If so, the question arises as to whether the other one-holed animals might have had two holes and lost them?
Evolution can be complicated and with all the new fossils and new tools to study it the coming decades should yield exciting findings as to how we got where we are and where we might be headed. As an example, let's turn to another hominin species that made news over ten years ago. This was the female "hobbit" found in a cave on the Indonesian island of Flores back in 2003. The little gal stood only about a meter tall and was deemed to be a new species and was given the name Homo floresiensis. The amazing thing about the discovery was that the sediments in which the fossils were found were dated to as recently as 18,000 years ago. The finding led to quite a bit of controversy, one factor being that modern humans arrived in that region of the globe about 50 or 60 thousand years ago and the implication was that they probably coexisted with the "hobbits". There were also claims that the hobbits were really just diseased homo sapiens.
In my April 1, 2016 issue of Science, I found an item referring to a paper in the journal Nature by a team of researchers including some of the same scientists who first discovered the hobbits. They have now analyzed sediments in the cave in an area where there are layers representing a clear time sequence and find that the hobbits actually lived back between 60 and a hundred thousand years ago, much earlier than the 18,000 figure, which now appears to have been in error. Thus there was no overlap between the little fellows and us moderns. Apparently, sediments used in the original dating were in a region of the cave where the sedimentary layers has been eroded into a sort of jumble. Although the new data seems to resolve the question about overlapping of those little people with us moderns, the question remains as to how and why they died out.
Unfortunately, it's all too clear as to why many other species of animal life are either extinct or dying out thanks to the presence and practices of us modern homo sapiens. At least some of our species recognize what we've done or are doing and are trying to stop and even reverse the trend. The May issue of National Geographic is devoted to Yellowstone National Park and the Yellowstone Ecosystem and describes attempts to attain a sort of reverse evolution to bring back the Yellowstone area to some semblance of the pristine environment before we humans started messing things up. Interestingly, one of our mistakes was killing off what Congress has just designated, in a bill awaiting Obama's signature, as our "National Mammal", the bison. Fortunately, the earlier mass slaughter of these animals was halted and now some 4,500 bison roam in Yellowstone. Wolves and beavers, were also either totally or mostly banished from Yellowstone but have been reintroduced or allowed to flourish.
The animal that draws most attention is the grizzly bear, especially on those rare occasions when a bear kills one of us humans. And we aren't even on the list of 266 items of the grizzly's diet. I've written before of my family's visit to Yellowstone back sometime in the 1960s. A neighbor had talked us into taking his tent with us on our auto trip out west. Our two young sons and I slept in the tent three nights, while my more sensible wife slept in the car. Each night we had a thunderstorm, one son was sick and bears were in the area. We saw one bear go up to a picnic table and make off with someone's food chest. We were admonished to eliminate all traces of food in our tent. Looking back, sleeping out there with bears all around was probably the stupidest thing I've ever done.
As indicated above, the grizzly's menu is quite large and includes some surprising things such as certain flowers. The item that most intrigued me is the army cutworm moth. This moth migrates into the mountainous area of Yellowstone every year. In this area the moth ingests lots of nectar from mountain wildflowers and by the end of the summer the critter is 60 percent or more body fat. Well, the grizzly has to build up its own store of body fat to see it through the winter and the cutworm moth is just the ticket. The bear will devour the moths, gobbling up as many as 40,000 a day! This corresponds to about 20,000 calories and helps fatten up the grizzly for the winter's hibernation.
Another item on the grizzly's menu is/was the cutthroat trout, native to the waters in Yellowstone. However, with the arrival of tourists and eager fishermen and a parasite new to the system, the cutthroat population suffered a major decline. Surprisingly, one big factor in the decline was the introduction by some unknown individual(s?) of another trout species, the lake trout, brought in from the Midwest. Turns out the lake trout is a predator of the first order. Not only does it dive deeper than the cutthroat trout but it eats other fish, such as the small cutthroat trout. Because it typically is deeper in the water the grizzly can't catch lake trout as easily as they did the cutthroat. Today the lake trout is considered such a pest that a company from Wisconsin has been hired to come in the Great Lakes style commercial fishing equipment in an attempt to kill off the lake trout, Doug Smith, in one of the Geographic articles, describes accompanying one of the outings to exterminate the lake trout and it's disturbing. By noon, they had killed over 200 lake trout, cutting each one open to check for eggs, puncturing their air bladders and then throwing them back in the water to preserve the nutrients in the system. Reversing evolution may not be easy or pretty.
Finally, you may have seen an item in the news this past week about another unwanted animal, this one appearing in an unusual habitat, the multibillion dollar 17-mile-long Large Hadron Collider (LHC) outside Geneva in Switzerland. After the acclaimed discovery of the Higgs boson, the LHC is ready to fire up again at higher power in hope of finding new particles. However, a weasel somehow wormed its way into a transformer that helps to power the LHC. The weasel is dead and, hopefully, the restart of the machine will only be delayed by a few days.
Next column, hopefully, on or about June 1.
Allen F. Bortrum
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