Sounds Very Fishy to me!
As reported in a previous blog, the issue of New Scientist dated 27 February 2008 carried a major article on intermediate or transitional forms in nature. It was written by Donald Prothero who is Professor of Geology at Occidental College in Los Angeles and lecturer in Geobiology at the California Institute of Technology in Pasadena. His book “Evolution: What the fossils say and why it matters” is published by Columbia University Press.
In this second blog item, we consider Professor Prothero’s suggestion that:
Another key transition in animal evolution was the appearance of the vertebrates. For more than a century, evidence has been accumulating from anatomy and embryology that the Chordata phylum (which includes the vertebrates) evolved from the echinoderms - sea urchins, starfish and their kin. This has now been corroborated by molecular biology. We also have an array of fossils and living organisms to tell the story of the transition.
Professor Prothero is dogmatic. Chordates (and therefore vertebrates) have evolved from echinoderm (spiny skin) ancestors. Although sea urchins and starfish fossils (and their kin) do not appear in Cambrian strata, there are some strange and extinct echinoderms. These include Edrioasteroids, eocrinoids and helicoplacoids.
In 2004, Shu and his team described another group of early Cambrian echinoderms, namely, the vetulocystids. In the same issue of Nature, Andrew Smith, Merit Researcher at the Natural History Museum in London, wrote a review of the Shu paper entitled “Echinoderm Roots”. The full article is available here. On the second page of this review, we see a figure of the main deuterostome groups.
Deuterostomes comprise a super phylum which encompasses the echinoderms and the chordates (including the vertebrates). You will notice from this diagram that Professor Prothero’s suggestion in the New Scientist that “the Chordata phylum (which includes the vertebrates) evolved from the echinoderms” is without any scientific foundation. Furthermore, Andrew Smith states in this Nature article:
There is now direct fossil evidence that all of the major deuterostome groups were established by about 520 million years ago. Fossil vertebrates (yunnanozoans), tunicates and both asymmetric and radiate echinoderms (homalozoans, helicoplacoids) have all now been discovered in early Cambrian deposits. Nevertheless Professor Prothero is insistent, chordates have evolved from echinoderms. Although there is no evidence for this in the fossil record, he suggests possible intermediate forms. These include hemichordates (e.g. acorn worms and filter feeding pterobranchs) and more particularly tunicates. He states categorically:
Next up are the sea squirts, or tunicates. Though adult sea squirts are similar to pterobranchs, the larvae look much like primitive fish, with a muscular tail supported by a "backbone" of cartilage, the notochord - the defining feature of the chordates.
Although this is somewhat confusing, the Professor states correctly that tunicates are classified as chordates since they possess a notochord (cartilaginous rod) but only in their juvenile form.
Chen reported the discovery of eight specimens of an early Cambrian fossil tunicate Shankouclava near Kunming (South China). The full paper is available here. Again the fossil record clearly indicates that there were tunicates in the early Cambrian. Accordingly, it is not possible to conclude on the basis of the actual evidence that tunicates have evolved from echinoderms or from anything else. It is simply inferred from the general appearance of extant forms of these phyla. Maybe this is an alternative updated example of "phylogeny recapitulates ontogeny" that was originally proposed by Ernst Haeckel on the basis of his dubious embryonic diagrams.
Nevertheless, appearances can be very deceptive. We recommend looking up an image of a tunicate larva and considering whether Professor Prothero’s suggestion that they “look like primitive fish” has any basis in reality. Nevertheless, he does not give up:
The transitional sequence continues with a group of obscure invertebrates called the lancelets. These resemble [emphasis added] tunicate larvae, and probably evolved from a tunicate-like creature through "neoteny" - retention of juvenile features in adulthood. With a notochord, muscular tail, gill slits, a digestive tract along the belly and many other chordate features, lancelets are the most fish-like invertebrates known. They have been around since the Cambrian: we have a number of good lancelet fossils such as Pikaia from the Burgess Shale and similar fossils from Chengjiang.
What is certain is that these fossil lancelets appear very similar to the modern and not so obscure amphioxus (a living example of a cephalochordate) which is alive and very well on planet Earth. The amphioxus is extremely common in shallow sandy environments such as Discovery Bay in Jamaica where up to five thousand individuals per square metre of sand have been reported. Amphioxus is commercially harvested and eaten by humans and domestic animals in some parts of Asia.
A question that is never answered is this: If lancelets are intermediate transitional forms leading to the evolution of vertebrates, why do they appear essentially unchanged after 500 to 600 million years of evolutionary time? In addition, when and how do lancelets move away from being lancelets to become something other? Again, the fossil record provides no help in answering these questions because representative fossils of all the particular groups are found in the same strata.
Needless to say, of particular interest are the ancient fish fossils that have been found in the Cambrian. For example, in 1999, Shu and his group reported the finding of two species of ancient jawless fish, namely, Haikouichthys ercaicunensis and Myllokunmingia fengjiaoa. A report of this discovery is found on the BBC website In this article, Professor Simon Conway Morris (University of Cambridge) is quoted as saying:
Until now, the early history of the fish has been extremely sporadic and sometimes difficult to interpret. This discovery shows that fish evolved much earlier than was thought. It indicates also that the rates of evolution in the oceans during the Cambrian period must have been exceptionally fast. Not only do we see the appearance of the fish, but also a whole range of different animal types.Also in 1999, Chen et al. reported the finding of another early Cambrian chordate which they called Haikouella lanceolata. In their paper, they state that Haikouella has evidence of:
a heart, ventral and dorsal aorta, an anterior branchial arterial, gill filaments, a caudal projection, a neural cord with a relatively large brain, a head with possible lateral eyes, and a ventrally situated buccal cavity with short tentacles. These findings indicate that Haikouella probably represents a very early craniate-like chordate that lived near the beginning of the Cambrian period during the main burst of the Cambrian explosion.
More recently, Shu reported further studies made possible by the discovery of numerous specimens of the early Cambrian vertebrate Haikouichthys ercaicunensis. The paper presents further evidence that Haikouichthys was a fossil agnathan.
Agnatha are jawless fish and are represented today by hagfish and lampreys. Professor Prothero admits to the presence of these ancient vertebrates in the Cambrian:
Cambrian rocks in China have also yielded fossils of the earliest-known vertebrates, the soft-bodied jawless fish Haikouella, Haikouichthys, and Myllokunmingia. These creatures did not yet have a hard bony skeleton, but have all the other features of jawless fish supported by a skeleton of cartilage.But then he says something quite remarkable and illuminating:
Placed in sequence, the acorn worms, tunicates, lancelets and soft-bodied jawless fish show the complete set of steps needed to evolve a vertebrate from an invertebrate ancestor.
We suggest that this very superficial assessment is circular reasoning. The sequence chosen is based on the assumption that the Darwinian hypothesis is true. The resulting sequence is then used as proof of the assumption. Furthermore, the suggestion by Professor Prothero that molecular biology corroborates his interpretation is similarly without support in the academic literature. For example, Frederick Delsuc and his co-workers published a paper in Nature in 2006. It’s worth reading the abstract!
So recent advances in molecular biology do not corroborate Professor Prothero’s imagined sequence and his is only one of many that could be constructed. It all sounds very fishy to me!
Top Evolutionist questions role of Natural Selection
One of the world’s leading evolutionary biologists has recently published a book which, as a central theme, questions the importance of natural selection in evolution.
Dr Michael Lynch is a distinguished Professor at Indiana University and one of the most influential figures in evolutionary genetics research. His CV lists 157 peer-reviewed scientific articles (to place this in context, it is over twice that of Richard Dawkins). In 2005, he wrote in a letter to Nature that "evolution is as much a fact as respiration and digestion” and dismissed intelligent design as “intellectual laziness".
Dr Lynch’s new book The Origins of Genome Architecture (Sinaeur, 2007) is a landmark professional text that seeks to apply evolutionary theory and population genetics to the study of whole genomes. Throughout the book, Lynch argues that the effectiveness of natural selection has been over-rated by many of his fellow evolutionists. For example, on page 367 of his book, Dr Lynch suggests that:
For the vast majority of scientists, evolution is nothing more than natural selection. This view reduces the study of evolution to the simple documentation of differences between species, proclamation of a belief in Darwin, and concoction of a superficially reasonable tale of adaptive divergence.
Lynch has several reasons for questioning the role of natural selection. In particular, the effectiveness of selection is very dependent on the size of the population it is acting upon: it is more effective in large populations than small ones. Smaller, simpler organisms (such as bacteria) tend to have much larger population sizes than larger, more complex organisms (such as mammals). So natural selection should be much less effective in mammals than in bacteria.
Instead of natural selection, Lynch suggests that much complexity has evolved passively. Due to the way in which organisms reproduce and mutations occur, complexity could gradually accumulate in biological lineages. Much of the book is devoted to explaining various non-adaptive mechanisms by which features of genomes could evolve.
That is not to say that natural selection is unimportant: Lynch still believes that it plays a major role in evolution. He considers that he is in the line of Darwin when he argues that natural selection should not be over-emphasised. He is concerned that the public may have been misled on this point:
Dawkins’s effort to spread the gospel of the awesome power of natural selection has been quite successful, but it has come at the expense of reference to any other mechanisms, and because more people have read Dawkins than Darwin, his words have in some ways been profoundly misleading (page 369).
He is equally critical of individuals involved in the education of children:
Numerous popularizers of evolution, some with careers focused on defending the teaching of evolution in public schools, are entirely satisfied that a blind adherence to the Darwinian concept of natural selection is a license for such activities (page 366).
He even suggests (on page 368) that:
the uncritical acceptance of natural selection as an explanatory force for all aspects of biodiversity (without any direct evidence) is not much different than invoking an intelligent designer (without any direct evidence).
The Origins of Genome Architecture received a glowing review in the leading science journal Nature on 14 February 2007. “This book is a must-read for every genome researcher,” wrote evolutionist Axel Meyer. He welcomed the controversial aspects of the book: “Not every evolutionary biologist, genome researcher or ‘evo-devo-ist’ will agree with Lynch's strong opinions that largely non-adaptive forces shaped genomes, but it is a debate worth having,” he wrote.
What Missing Link?
The issue of New Scientist dated 27 February 2008 carries a major article on intermediate or transitional forms in nature. It is written by Donald Prothero who is professor of geology at Occidental College in Los Angeles and lecturer in geobiology at the California Institute of Technology in Pasadena. His book “Evolution: What the fossils say and why it matters” is published by Columbia University Press.
In this article, Professor Prothero cites 10 examples to demonstrate the concept of a transitional form and to reinforce the idea that the fossil record provides evidence for the Darwinian hypothesis. The first of these examples are the velvet worms which belong to the phylum Onychophora, meaning 'claw-bearers'. At least eighty living species are known comprising two families, namely, the Peripatidae and the Peripatopsidae. They are found in tropical or sub-tropical regions of the Americas, Africa, South Eastern Asia and Australasia, which has the greatest variety.
The Onychophora first appear in the fossil record in the Cambrian Explosion. This geological event presents a significant problem for Darwinism since around half of the major animal phyla appear in the fossil record fully formed without any fossilised ancestors. This is how Richard Dawkins describes it in “The Blind Watchmaker” (page 229):
The Cambrian strata of rocks, vintage about 600 million years, are the oldest ones in which we find most of the major invertebrate groups. And we find many of them already in an advanced state of evolution, the very first time they appear. It is as though they were just planted there, without any evolutionary history. Although there have been more suggestions that the Onychophora are intermediate between annelids (segmented worms) and arthropods (a phylum including crustaceans and insects), according to Professor Prothero:
A classic example of a transitionary form links the arthropods to the lineage they split from in the Cambrian, namely, the nematode worms. These are the "velvet worms" or Onychophora. In many respects, the velvet worms resemble nematodes, but they also have key attributes of the arthropods - most notably segmented legs that end in hooked claws. They also have many other features found in arthropods but not nematodes, including an outer layer made of chitin, which they moult on a regular basis, antennae, compound eyes and arthropod-like mouthparts.
Unlike other scientists, Professor Prothero suggests that the velvet worms are derived from nematodes (roundworms) which are one of the most common phyla of animals, with more than 20,000 living species. Fossil nematodes are relatively rare but they do exist. The best examples of ancient nematodes have been found preserved in amber and dated from the Cenozoic period. Another example is a putative nematode (Captivonema cretacea) from the early Cretaceous. Whether nematode fossils will ever be found in Cambrian (or pre-Cambrian) strata remains to be seen and according to Simon Conway Morris:
To date, however, the fossil record throws no useful light on the origin of the nematodes. [Conway Morris S. (2004) Darwin’s Dilemma: The realities of the Cambrian Explosion Philosophical Transactions of the Royal Society. 361: 1069–1083].One of the reasons suggested for the absence of nematode fossils in Cambrian strata is their microscopic size and possession of soft body parts. Nevertheless, current research suggests that at least part of the Cambrian strata was laid down very rapidly [see Gabbott SE et al. (2008) Journal of the Geological Society; 165: 307-318]. This at least explains the amazing fossil preservation of myriads of soft bodied creatures.
Soft tissue fossils have also been found in the Cambrian strata from Chengjiang, near the city of Kunming in Yunnan Province, China. Apart from a vast array of arthropods, representatives of Lobopoda, small segmented animals resembling (and maybe including) Onychophora, have been found in these mudstone sediments. In addition, several examples of Nematomorpha have been discovered. These creatures are similar to Nematodes but are a distinct phylum with many modern representatives such as the horsehair worms.
So Professor Prothero’s suggestion that the Onychophora are transitional between nematodes and arthropods cannot be borne out by the actual evidence presented in the fossil record. It is based on the rather superficial assessment that “velvet worms resemble nematodes”. He concludes this section of his article by stating:
You could not ask for a better "missing link" between the nematodes and the arthropods, except it's not missing - we've known about velvet worms for over a century in both the living fauna and the fossil record.
Although this statement is somewhat misleading, at least the Professor highlights the fact that Onychophora might be considered “living fossils”. The ancient Cambrian species Aysheaia seems remarkably similar to the modern Peripatus.
In future blogs, we will consider some of Professor Prothero’s other examples.
An Echo from the Past
The current edition of New Scientist (16th February) carries a small report entitled “Earliest Bats had no use for echos”. The article describes the work of Nancy Simmons of the American Museum of Natural History (New York) and her team who found the fossil of an ancient bat (Onychonycteris finneiyi) in the Green River Formation in Wyoming. Their work has been published in detail in the journal Nature [Nature 451: 818-821 (14 February 2008)]. In the words of the authors of this paper:
The Green River Formation of Wyoming has produced many spectacular fossils, including Icaronycteris index, widely regarded as the oldest and most primitive known bat. Icaronycteris comes from the Fossil Butte Member of the Green River Formation, late early Eocene epoch, about 52.5 Myr ago. Recently a new bat was discovered in the Fossil Butte Member that differs from Icaronycteris and other Eocene bats in being larger, having more primitive limb proportions and basicranium, and possessing well-developed claws on all wing digits. Because it cannot be assigned to any existing taxon, we here describe it as a new family, genus and species.
Bats are unique among mammals as they possess the ability to fly and, in many cases, the ability to catch their prey using echolocation. Technically, bats are included in the order Chiroptera (meaning hand-wing) which is the second largest mammalian order with 966 species identified to date. There are two suborders, the Megachiroptera (megabats) and the Microchiroptera (microbats). All of the megabats belong to the same family (Pteropodidae) which includes the Old World fruit bats or flying foxes. The microbats are distributed across four superfamilies (17 families in total).
Richard Dawkins has devoted an entire chapter on echolocation in bats in “The Blind Watchmaker”. This is a useful overview of this remarkable phenomenon. In the second chapter, entitled “Good Design”, he writes: "Not all bats use echolocation. The Old World tropical fruit bats have good vision and only use their eyes for finding their way around." [The Blind Watchmaker (1991) London: Penguin p.24]
In fact, megabats have large eyes and exceptionally good colour eyesight, similar to the vision of an owl at night. All bats are mainly nocturnal, microbats rely on echolocation to catch their prey whereas most megabats rely on their eyesight and other senses. As Professor Dawkins rightly points out, there are a few exceptions. An example is the Egyptian Fruit bat (Rousettus aegyptiacus) which also uses low pitched sounds and echo location in addition to its eyesight.
Characteristic of echo-locating bats is the increased size of the inner ear (cochlea) together with the associated complex neuroanatomy of the brain stem. According to the Nature article, O. finneyi possessed a relatively small cochlea similar to that seen in modern non-echolocating bats (Pteropodidae). In addition, the New Scientist suggests:
... it lacked the special ear-bone modifications needed for echolocation - the ability to use reflected sound to find and identify objects while flying - and probably flew "deaf".
This of course is total nonsense as the article goes on to include the following quote from Nancy Simmons: If the bat is listening out for sounds of “crashing insects” it can hardly be flying “deaf”.
Without echolocation, Onychonycteris would probably not have been good at catching insects in flight, though it might have used vision or smell to help find insect prey. Like some modern bats, it might also have used ‘passive audition’, such as listening out for sounds that insects make when they crash into vegetation.
The feature that seems to mark out O. finneyi as different is the fact that it possessed teeth characteristic of an insectivore. Modern megabats, however, can and do eat insects as an extra source of protein [see SE Courts Dietary Strategies of Old World Fruit Bats: how do they obtain sufficient protein? Mammal Review (1998) 28:185].
And so the Green River formation continues to yield up its treasures. Within the same strata have been found fossil fish, insects, snails, turtles, crocodiles, birds, and plant remains. The new discovered species (Onychonycteris finneiyi) is now added to the list of mammals that also includes another ancient bat (Icaronycteris index).
Without any justification, New Scientist concludes as follows: The fact of the matter is that both echolocating and non-echolocating bats exist today and this seems to have been the case in ancient times as illustrated by the Fossil Butte sediments in Wyoming. The evidence clearly suggests that these ancient bats co-existed. They are an echo from the past.
but it was not long before echolocating bats replaced O. finneyi. Fossils of another bat, Icaronycteris index, found in the same rock, have skull bones consistent with echolocation [emphasis added].