Archive for the 'Evolution' Category

Jul 18 2017

More on Junk DNA

Published by under Evolution

Junk-VennJunk DNA, put simply, is those parts of the genome (human or otherwise) that have no known function. The human genome has about 19,000 genes. A gene is essentially a sequence of base pairs that code for a protein – there are four difference bases with each triplet being a “word” that either codes for an amino acid or tells the process of transcribing the protein to stop.

Even within genes there are noncoding regions, called introns, which have to be removed from the RNA so that the coding regions can be joined together. Between the genes there are also vast non-coding regions. Some of this non-coding DNA is regulatory and structural – it helps regulate when and how much specific genes are transcribed into proteins.

The burning question is, how much of the non-coding regions between the genes serves any function and how much is completely unnecessary, or “junk”? This is an important question for understanding genetics, but also has implication for creationists. Creationists don’t like the concept of junk DNA because it strongly implies an evolutionary history. Why would a designer sloppily insert so much unneeded junk into our pristine genome? Why are genes clogged with non-coding regions that need to be removed? So they claim that all DNA has function, we just don’t know what it is.

ID proponent Stephen Meyer, for example, said:

“For example, we predicted very early on that the junk DNA was not junk. We did that on the basis of an ID perspective. “

Continue Reading »

63 responses so far

Jun 12 2017

Earliest Modern Human

Published by under Evolution

Jebel Irhoud skullLast month I wrote about Graecopithecus, a possible human ancestor from just after the split with chimpanzees about 7 million years ago. Also last month it was reported that an analysis of new Homo naledi specimens dates the fossils from as recently as 236 thousand years ago. H. naledi share some primitive features that paleontologists thought would date to about 2 million years old, but they also have some more modern features.

In April I also wrote about the latest study of H. floresiensis (the Hobbit) showing that it is very likely this was indeed its own species.

All of these news items share a theme – that the picture of the evolution of modern humans from our last common ancestor with chimpanzees is likely much more complicated than we currently know and previously suspected. I think the analogy of a jigsaw puzzle is apt. We are trying to piece together this puzzle, but we don’t know what the final picture looks like. We are connecting lines to the pieces we have, but when we find more evidence we are not just filling in the picture, we are expanding it.

Our map of how human evolution proceeded was just a best fit to the existence evidence. We are still in a stage of our discovery where every new major find alters that best fit. This process was inevitable as we started with a maximally simple (and naive) map – a linear progression from apes to humans. Now we know, as with pretty much every other evolutionary tree, the real map is much more bushy. Adaptive radiation lead in multiple directions simultaneously, only one branch of which survived to be modern humans.

Homo Sapiens from Jebel Irhoud Continue Reading »

2 responses so far

May 23 2017

Graecopithecus – Possible Early Human Ancestor from Europe

Published by under Evolution

graecopithecusFinding fossils is like finding pieces to a jigsaw puzzle, although we don’t know what the final picture is, or where the edges are, and the pieces themselves are damaged or partial and so it is not always clear if they fit. A piece may seem to fit in one location, but it actually goes somewhere else. Sometimes one section of the puzzle can come together, but you are still not sure where it fits into the greater puzzle. But eventually a clear picture can emerge.

For the last century paleontologists have been trying to piece together the puzzle of human evolution. It’s hard to say how close we are getting to having a reasonably complete picture, because again we don’t know how big the puzzle is or where the edges are. One way to get a sense of where we are is this – with each new fossil find is the puzzle getting bigger and more complex or are we filling in known gaps? It’s definitely some of both, but mainly the puzzle is still getting bigger. We don’t know yet how much we don’t know. We’re not just connecting the dots, we keep adding new dots.

A recent analysis of one potential hominin makes the picture more complex still. Graecopithecus is known from a lower jaw and an upper pre-molar. That is not much, which is why the papers on this fossil all describe is at a “possible” early human ancestor. If Graecopithecus turns out to be legit, then it would be the oldest human ancestor after the split with chimpanzees, and it would move the likely location for that split from sub-Saharan Africa to the Mediterranean.

Continue Reading »

261 responses so far

Apr 25 2017

New Study of The Hobbit

Published by under Evolution

HobbitI have been following the story of Homo floresiensis for the last decade, and it is fascinating. The remains of a diminutive humanoid were found on the island of Fores in Indonesia. The remains date to about 54,000 years ago. The findings immediately sparked debate, with two primary schools of thought emerging.

The first hypothesized that H. foresiensis (nicknamed the Hobbit due to their small size) was a new species of hominin, likely evolve from H. erectus and displaying an example of island dwarfism. The second argued that the remains are not a new species at all and represent a pathological H. sapiens (modern human).

The two groups have argued back and forth in the scientific literature over the years. It is, in fact, a great example of the scientific method in action. Each group brought new evidence and a new perspective to bear, and had the burden of proof to demonstrate their hypothesis. They fought it out with science and evidence.

I and many others sat of the sidelines and watched the epic battle of science. I admit I was rooting for H. floresiensis, but we would all have to listen to the evidence, whatever it showed.

It’s also a good example of the limitations of mainstream science reporting. Each time a study was published, favoring one side of the debate or the other, it was reported as if the debate were finally over and now we know the answer. Instead they should have put that one study into context – this is just another round in an ongoing debate. The fight isn’t really over until one side concedes defeat and a consensus emerges. Even then, new evidence may trump the consensus, but at least we have a consensus rather than a controversy.

The New Study Continue Reading »

10 responses so far

Mar 27 2017

More on Bird Evolution

bird_evoThe fossil evidence for the evolution of birds is currently one of the greatest evolutionary stories we have to tell. It is also a home run for the predictive value of evolutionary theory and is a devastating blow to any denial of common descent.

Darwin published On the Origin of Species in 1859. At that time the fossil record was sparse, although it was enough to establish that the forms of living things was changing over geological time. One of the most dramatic gaps in the fossil record at the time was between birds and other vertebrates. It was believed that birds must have evolved from some type of reptile, but the most recent common ancestor was not known.

This was a great test for the new theory of evolution. If evolution were true then birds must have evolved from something else, and therefore the gap between birds and their closest non-avian relative should eventually be filled in by future fossil finds. If evolution is true, those creatures must have existed.

If, on the other hand, some version of creationism were true so that was created close to its current form, then there would not have to be any creatures filling in the morphological space between birds and their closest relatives. Birds would not have any relatives, they would be an isolated group unto themselves.

Continue Reading »

111 responses so far

Dec 13 2016

Feathered Dino Tail Trapped in Amber

amber-feathered-tail2Lida Xing from the China University of Geosciences in Beijing was walking through an amber market in Myitkina, Myanmar when he discovered a rather interesting specimen. The seller believed that the large chunk of fossilized tree sap they were selling contained plant material. Xing recognized that it contained primitive feathers. Even more exciting, those feathers were not connected to a bird ancestor, but to the tail of a dinosaur.

A scientific analysis of that specimen has now been published in Current Biology.

This is a tremendous specimen for a number of reasons. Scientists interested in the evolution of feathers have been trying to piece together the developmental steps that occurred and in what order in order to transform scales into feathers. Developmental biology itself provides some clues – the path that feathers take when they develop in the embryo likely reflect their evolutionary history. It would be nice, however, to confirm this hypothesis with actual specimens.

Up until now paleontologists have had two kinds of fossil feathers. The first is feather impressions associated with fossil specimens. The advantage of this kind of evidence is that we know exactly what species the feathers belong to and so they can be placed in a phylogenetic tree of feathered dinosaurs, both avian and non-avian. The disadvantage is that the feather impression are compressed, so the three-dimensional information may be lost, and they often lack fine detail.

Continue Reading »

11 responses so far

Sep 19 2016

Bacteria Evolving Resistance

Researchers at Harvard did a clever thing. They created a giant plate on which to grow bacteria, and included in the plate increasing concentrations of an antibiotic as you moved toward the center. They then plated bacteria on the outer edges and made a time-lapse video of the bacteria growing.

The end result was a video showing the evolution of progressive antibiotic resistance in the bacteria. You can actually see adaptive radiation, as the bacteria push up against the boundary to the next higher concentration of antibiotics, then multiple locations start to spawn new colonies spreading in the next zone.

The researcher made some more nuanced observations as well. For example, the bacterial grow slowed with new mutations, meaning they sacrificed something with the resistance mutation, but then they sped up again as they further evolved. Further, the most resistant bacteria were often not at the leading edge but were stuck behind less resistant bacteria.

Continue Reading »

729 responses so far

Aug 05 2016

Mike Pence Does Not Understand Evolution

Pence-EvolutionIt is my universal experience, after more than thirty years of confronting various forms of evolution denial or creationism, that creationists simply do not understand evolution. If any do understand it, they pretend not to. I guess they have no choice – they are motivated to deny an established scientific theory. They need to pretend they know better than the world’s experts, or that the world’s experts are lying and deceitful.

Mike Pence is a run-of-the-mill creationist. His denial of evolution is unremarkable and unimaginative, but now he is running for Vice President so his views serve as a ripe target for criticism. In a speech before the House he decided, for some reason, to go on a rant against evolution. For those who are interested, it is a good opportunity to play “name that logical fallacy” and you may want to watch the video and count the errors before reading ahead.

Pretty much everything Mike Pence says in the speech is wrong or misleading, except for trivial facts. He starts by setting the stage with Darwin publishing On the Origin of Species and presenting the theory of evolution. That evolution is just a “theory” is a main theme of his speech, which I will get to in a moment, but first he follows up by saying that Darwin expected his theory to be proven correct by the fossil record. He concludes that Darwin did not live to see this happen, and neither have we.

Is Evolutionary Theory Proven? Continue Reading »

1,049 responses so far

May 27 2016

A Tale of Two Science News Reports

parviceps

One of the recurring themes of this blog, and of the skeptical movement itself, is that science news reporting is generally poor. It is highly variable – there are some excellent science news reporters out there, but most are mediocre and some are terrible. The problem is that the average quality is simply too low.

The problem is compounded by the fact that scientists sometimes overhype or overinterpret their results, but even more common, the press office for the university at which the scientists work often sensationalize the science. At every step there is an opportunity to add hype, misinterpret the actual results, sensationalize, focus on the speculative aspect of the study rather than the actual data, or simply get the story wrong.

The race for clicks seems to be driving the quality of science reporting down, favoring clickbait headlines. Reporters don’t seem to mind getting the story wrong and then being corrected by science bloggers, for then they just get another round of clicks correcting their own bad reporting as if it were someone else’s fault.

Sclerocormus parviceps Continue Reading »

16 responses so far

Apr 08 2016

Answering Creationist’s Unanswerable Questions

creationist-videoPointing out how completely illogical and unscientific are creationists is something I need to do on a regular basis here. A creationist who regularly trolls the SGU Facebook page recently posted this video, which is a great opportunity to meet my creationist debunking quota.

Like all creationist propaganda, the video does not make any serious or legitimate scientific points. The purpose is just to provide a plausible screen for denying one of the most solid scientific facts every established – that life on Earth is the product of organic evolution.

The video is a collection of “gotcha” ambushes of students and scientists, asking them loaded questions that defy a simple answer (because first you would have to unpack all the false assumptions in the question itself). It’s natural to pause after such a question, while considering how best to approach it. The segments often cut out after the initial partial response followed by a “gotcha” follow up statement by the interviewer.

Continue Reading »

17 responses so far

Next »