Sunday, 5 November 2017

Yes, We Were There

Yes, We Were There

 Antoine Bret

Many believe that to inform us about the past, science depends on an assumption of uniformitarianism: that the laws of nature we know today were the same in the past. Creationist literature often argues that faith in this “stability principle” is misplaced. For example, the starlight argument, observing that light arriving from stars farther than 6 000 lightyears must have been created more than 6 000 years ago, is attacked this way. Creationists will reason that the argument is only sound if light has always been traveling at its current speed. But if light traveled faster in the past, objects farther than 6 000 light-years away could have been created only 6 000 years ago and yet still be able to send us light. Barry Setterfield became famous in creationist circles in 1981 by “scientifically” exploring the idea (Setterfield 1981).

Radioactive dating methods used to determine the age of Earth, or of the universe, are attacked from the same angle. The uranium–lead dating technique, for example, is instrumental in dating our planet. It relies on the stability of the decay rates involved in the uranium–lead decay chain. How can we be sure these rates have been the same in the past? Can we observe the past? Doubts in clearing up these issues lead to Ken Ham’s rhetorical question “Were you there?”

Sunday, 22 October 2017

Heterochronic evolution explains novel body shape in a Triassic coelacanth from Switzerland

Heterochronic evolution explains novel body shape in a Triassic coelacanth from Switzerland

Lionel Cavin, Bastien Mennecart, Christian Obrist, Loïc Costeur & Heinz Furrer

Scientific Reports 7, Article number: 13695 (2017)  


A bizarre latimeriid coelacanth fish from the Middle Triassic of Switzerland shows skeletal features deviating from the uniform anatomy of coelacanths. The new form is closely related to a modern-looking coelacanth found in the same locality and differences between both are attributed to heterochronic evolution. Most of the modified osteological structures in the new coelacanth have their developmental origin in the skull/trunk interface region in the embryo. Change in the expression of developmental patterning genes, specifically the Pax1/9 genes, may explain a rapid evolution at the origin of the new coelacanth. This species broadens the morphological disparity range within the lineage of these ‘living fossils’ and exemplifies a case of rapid heterochronic evolution likely trigged by minor changes in gene expression.

Wednesday, 11 October 2017

Peter Harrison - Why religion is not going away and science will not destroy it

In 1966, just over 50 years ago, the distinguished Canadian-born anthropologist Anthony Wallace confidently predicted the global demise of religion at the hands of an advancing science: ‘belief in supernatural powers is doomed to die out, all over the world, as a result of the increasing adequacy and diffusion of scientific knowledge’. Wallace’s vision was not exceptional. On the contrary, the modern social sciences, which took shape in 19th-century western Europe, took their own recent historical experience of secularisation as a universal model. An assumption lay at the core of the social sciences, either presuming or sometimes predicting that all cultures would eventually converge on something roughly approximating secular, Western, liberal democracy. Then something closer to the opposite happened.

Not only has secularism failed to continue its steady global march but countries as varied as Iran, India, Israel, Algeria and Turkey have either had their secular governments replaced by religious ones, or have seen the rise of influential religious nationalist movements. Secularisation, as predicted by the social sciences, has failed.

Sunday, 24 September 2017

What's new at Christadelphian - Origins Discussion

It's heartening to see other Christadelphian Internet sites discussing both evolution, and how to understand our faith tradition in the light of the fact of common descent and large-scale evolutionary change. One of these, Christadelphian Origins Discussion has recently added a webpage, which includes a number of posts on subjects ranging from common descent to refuting and correcting common Christadelphian misunderstandings on evolution to ancient Hebrew cosmogeography. Definitely a website to add to your bookmarks.

Friday, 22 September 2017

Where's the Evolution? Why, here!

One of the more common tactics evolution denialists employ is to juxtapose photographs of fossils and contemporary organisms, and claim that the apparent absence of change means evolution never occurred. There are many fundamental problems with this problem, such as the fact that poor quality photographs of fossils fail to pick up the subtle morphological details that are apparent when the actual fossils are examined, morphological stability in environments where there are no strong selective pressures, not to mention the fact that even in the absence of marked morphological change, there will nonetheless be strong evidence of change at the genomic level which is of course not apparent in a grainy photograph.

Arguably the most notorious proponent of this deceptive tactic is the Turkish evolution denialist Adnan Oktar, otherwise known as Harun Yahya. Oktar is hardly alone, with many special creationists using this approach to attack evolution. One example is the Facebook page Where is the evolution? which has in turn triggered the creation of another page Here is the evolution, which exposes the intellectually vacuous approach of their approach by focusing on the fundamental concept of evolution - descent with modification produces an evolutionary tree.

Friday, 25 August 2017

How Molecular Clocks Are Refining Human Evolution's Timeline

How Molecular Clocks Are Refining Human Evolution's Timeline

By Bridget Alex and Priya Moorjani

This article was originally published at The Conversation and has been republished under Creative Commons.

DNA holds the story of our ancestry—how we’re related to the familiar faces at family reunions as well as more ancient affairs: how we’re related to our closest nonhuman relatives, chimpanzees; how Homo sapiens mated with Neanderthals; and how people migrated out of Africa, adapting to new environments and lifestyles along the way. And our DNA also holds clues about the timing of these key events in human evolution.

When scientists say that modern humans emerged in Africa about 200,000 years ago and began their global spread about 60,000 years ago, how do they come up with those dates? Traditionally researchers built timelines of human prehistory based on fossils and artifacts, which can be directly dated with methods such as radiocarbon dating and Potassium-argon dating. However, these methods require ancient remains to have certain elements or preservation conditions, and that is not always the case. Moreover, relevant fossils or artifacts have not been discovered for all milestones in human evolution.

Analyzing DNA from present-day and ancient genomes provides a complementary approach for dating evolutionary events. Because certain genetic changes occur at a steady rate per generation, they provide an estimate of the time elapsed. These changes accrue like the ticks on a stopwatch, providing a “molecular clock.” By comparing DNA sequences, geneticists can not only reconstruct relationships between different populations or species but also infer evolutionary history over deep timescales.

Molecular clocks are becoming more sophisticated, thanks to improved DNA sequencing, analytical tools, and a better understanding of the biological processes behind genetic changes. By applying these methods to the ever-growing database of DNA from diverse populations (both present-day and ancient), geneticists are helping to build a more refined timeline of human evolution.

Sunday, 23 July 2017

Nothing in Medicine Makes Sense Except in the Light of Evolution

The title of this post is a direct allusion to Theodosius Dobzhansky's famous 1973 article Nothing in Biology Makes Sense Except in the Light of Evolution [1] in which he outlined facts from areas such as ecology and molecular biology, and stated that "all these remarkable findings make sense in the light of evolution: they are nonsense otherwise." In a similar manner, aspects of human anatomy, developmental biology, physiology, and genetics which look bizarre, poorly designed, and otherwise defy rational description (not to mention difficult to memorise and store for quick recall) become perfectly understandable when understood in the light of an evolutionary origin for the human species. Examples include extra nipples along the milk line [2], the inverted retina [3], the multiple  pseudogenes, retrotransposons, and endogenous retroviral elements we share with primates [4], not to mention the presence of non-coding intronic DNA, which leads to mutations at intron-exon borders that "often disrupt premRNA splicing in ways that alter gene products and lead to countless genetic disabilities, including various cancers and other metabolic defects." [5]

I am not the first to allude to Dobzhansky in reflecting on the increasing importance evolution has for both understanding the basic clinical sciences on which medicine is based, and for the practice of medicine itself. Ajit Varki, Distinguished Professor of Medicine and Cellular & Molecular Medicine at the University of California,  San Diego wrote in 2012 a paper with the same title as this post where he states that the 'scientific aspects of medicine are rooted in understanding the biology of our species and those of other organisms that interact with us in health and disease. Thus, it is reasonable to paraphrase Dobzhansky, stating that, 'nothing in the biological aspects of medicine makes sense except in the light of evolution'" and proceeds to outline his experience in teaching evolution to medical students. [6] Given that there are more than 4.7 million hits in Google Scholar when searching for evolution and medicine, Varki's desire (and that of many other physician and scientists) to integrate evolutionary biology in the teaching of medicine is eminently sensible.