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Binocular Vision

4 February 2012, 3:44 am

Binocular vision is the ability to direct both eyes simultaneously at an object. In considering the evolution of man it was coupled with manipulating hands in early primates and is considered basic to the development of intelligence. The importance of this ability for the growth of the brain is that it allows a better judgment of distance, valuable for leaping and throwing. It stimulates three dimensional thinking. The evolution of manufacturing levels of intelligence requires the development of hand and eye coordination. Without the ability to see stereoscopically, it seems unlikely that it would be possible to think stereoscopically and thereby to erect structures in the mind prior to building them on the ground. Many creatures alive today besides man have binocular vision, birds of prey like the owl, for instance, but they do not often combine it with grasping hands.

Binocular Vision in a Dinosaur like a Troodon

Binocular vision in tyrannosaurus was facilitated by the snout being very narrow so as not to impair its line of sight. But tyrannosaurus, as we have seen, had atrophied arms and the real evolutionary advantage comes when the binocular vision is combined with skillful hands. The troodon (stenonychosaurus) had binocular vision combined with manipulative hands and fingers. Its eyes were large and well developed like the eyes of the ostrich—which has the largest eyes of any terrestrial creature alive today. This in itself is an interesting feature because it suggests that these dinosaurs were nocturnal or that they had evolved not long before from a nocturnal form.

Two points from this. First, it is further evidence, should anyone need convincing, that the dinosaurs were warm-blooded, because cold-blooded animals must be inactive at night. Second, what would they be hunting at night time that needed speed, agility, keen vision and grasping hands? None other than our predecessors, the mammals. Desmond puts it like this:

It was not until the Cretaceous that we find signs that the mammals were hounded even into the night. They were terrorized, moreover, by creatures more cunning than themselves.

Yes, the mammals were small, but these dinosaurs were also small by dinosaur standards—stenonychosaurus was only about five feet long including its long tail. Here then is a dinosaur with keen senses, nimble and agile enough to hunt, by night, the supposedly superior mammals!

Originally posted 2009-06-05 23:00:27. Republished by Blog Post Promoter

Filed under Anthroposaurus sapiens, Dinosaurs. Tagged , , ,
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Stamp Out the Unethical Practices of some Journal Editors

4 February 2012, 1:27 am

Dr Allen W Wilhite, and Dr Eric A Fong analyzed 6,672 responses from a survey sent to researchers in the fields of economics, sociology, psychology, and business. Many journal editors in these fields require authors to add extra citations to the journal publishing the work. The editors that indulge in this practice even target certain authors, such as assistant and associate professors, rather than full professors, relying on the fact that lower ranking authors may be more willing to add the spurious citations. While most authors disapprove of the practice, many feel they have to agree or risk being rejected.

Journals

Wilhite and Fong have brought to light this unethical practice, which damages academia and the integrity of academic publications. It is cheating, and ultimately can alter careers, the cheats favorably, and those who refuse to comply adversely. Professional associations ought to stamp it out quickly.

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The Permian Mass Extinction was not Instantaneous, but was Still Sudden, Geologically

4 February 2012, 12:58 am

The National Science Foundation (NSF) reports research showing the deadliest mass extinction of all—“The Great Dying” or the Permian-Triassic extinction 252 million years ago at the end of the Permian period, which killed 90 percent of Earth’s marine life—took a long time to do it, and it did it in stages. So, mass extinctions need not be “sudden” events. Thomas Algeo, a geologist at the University of Cincinnati, and 13 colleagues have produced a high-resolution look at the geology of a Permian-Triassic boundary section at Griesbach Creek on Ellesmere Island in the Canadian Arctic. They offer strong evidence that Earth’s biggest mass extinction phased in over hundreds of thousands of years.

Numbers of Marine Families Plotted across the Permian-Triassic Boundary

Algeo and colleagues have spent much of the past decade investigating the chemical evidence buried in rocks formed during this major extinction. The world revealed by their research is a devastated landscape, barren of vegetation and scarred by erosion from showers of acid rain, huge “dead zones” in the oceans, and runaway greenhouse warming leading to sizzling temperatures. Massive volcanism in Siberia, the volcanic eruptions which created the Siberian Traps, seems to have been the cause.

The Siberian Traps were formed by one of the largest known volcanic events of the last 500 million years, continued for a million years, and spanned the Permian-Triassic boundary. They cover a large region of Siberia, an area as big as the continental United States, and consist of vast amounts of lava spewed out for hundreds and thousands of years by an exploding supervolcanic hotspot. These deposits, which can be five kilometers (three miles) thick, are called traps from the Swedish for stairs, trappa, because the eroded lava looks like stairs on the surface of the earth.

Situation of the Explored Site in Relation to the Siberian Traps 252 Million Years Ago

As if the sheer size of the eruptions was not enough to pollute the earth, the lava flowed through a large coal deposit, oxidizing by its heat the coal and creating huge quantities of methane, a greenhouse gas 30 times more effective than carbon dioxide. How long the ensuing greenhouse effect lasted is not known but it seems to have been tens or hundreds of thousands of years.

Much of the evidence was washed into the ocean, and Algeo and his colleagues look for it among fossilized marine deposits. Previous investigations have focused on deposits created by a now vanished ocean known as Tethys, a precursor to the Indian Ocean. Those deposits, in South China particularly, record a sudden extinction at the end of the Permian. Algeo explained that this is why the extinction was thought to have been quick, geologically speaking:

In shallow marine deposits, the latest Permian mass extinction was generally abrupt. Based on such observations, it has been widely inferred that the extinction was a globally synchronous event.

From rock layers found at West Blind Fjord on Ellesmere Island in the Canadian Arctic, a location that, at the end of the Permian, would have been much closer to the Siberian volcanoes than sites in South China, Algeo and his team measured the sedimentary rock layers as 24 meters (almost 80 feet) thick, and found they crossed the Permian-Triassic boundary, including the last Permian mass extinction. The investigators looked at how the type of rock changed from the bottom to the top, and at the chemistry of the rocks and at the fossils contained in the rocks.

They discovered a total die-off of siliceous sponges about 100,000 years earlier than the marine mass extinction event recorded at Tethyan sites. It seems the effects of early Siberian volcanic activity, such as toxic gases and ash, were confined to the northern latitudes. Only after the eruptions were in full swing did the effects reach the tropical latitudes of the Tethys Ocean. So what was thought to have been geologically instantaneous actually took more than 100,000 years. That, however, is still geologically sudden, and so the die off still counts as a mass extinction.

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Was Majungasaurus a Terrestrial Vulture Adapted to Consume Carcases from the Inside?

1 February 2012, 4:09 am

First discovered in 1895, Majungasaurus crenatissimus became well known through hundreds of fossils recovered by the joint Mahajanga Basin Project of Stony Brook University and the Université d’Antananarivo between 1993 and 2007. Its powerful jaws bristled with bladelike teeth, and its strong legs terminated in formidable claws. Though nearly every detail, from its cranial sinuses to an injury on its tail, has been noted, its forelimbs remained a mystery. A new study has examined them closely, and they are odd. Indeed, many features of Majungasaurus are peculiar. It is a remarkably atypical theropod.

Majungasaurus

Majungasaurus is an abelisaurid, a group of theropod dinosaurs known to have inhabited Gondwana, the massive southern continent before plate tectonics caused it to split into several different smaller continents, South America, Africa, India, Australia and Antarctica.

Lead author, Sara Burch, of Stony Brook University, says:

The proportions of this limb are unlike anything we see in other theropods.

Majungasaurus forelimbs

The forearm bones are short, only a quarter of the length of the humerus, the upper arm bone, but extremely thick set. The wrist bones are not ossified, and the four stubby fingers seemed not to have claws. The thick forearm bones and the stubby fingers look like a sort of modified hand. Short arms are typical of several large theropods, Tyrannosaurus rex, for example. The arms of these animals apparently were of no use in the hunting strategies of these animals. On the other hand, birds are descended from theropods, but in them the forelibs have evolved into wings, albeit with loss of some digits.

T rex forelimbs, short but directed forewards

Burch explained further:

While many theropods have reduced limbs, most retain their normal proportions. We don’t know of any other case where the forearm bones have become more robust in this way. Abelisaurids like Majungasaurus were clearly on a completely different trajectory from the lineage leading to birds.

It is hard to imagine how Majungasaurus’s stubby forelimb was used, but, grasping was impossible, and nor could the individual digits have moved independently. This animal was not doing much manipulation with such a stubby hand, though the joint anatomy suggests great mobility at the elbow and wrist. The limb may have been used in display, or be an unknown evolutionary path cut short by the K-T extinction, but this morphology was quite widespread throughout Gondwana during the Late Cretaceous. What is needed is an hypotheses of how this bizarre forelimb evolved.

Recnstructions of the skeleton of Majungasaurus from the many fragments found yield an oddly proportioned animal with large powerful legs which seem badly positioned for stability, the front part of the animal looking bigger and heavier than the tail, though the tail could have had powerful muscles attached to power the strong looking rear limbs, so it is hard to be sure. The neck though is also peculiarly long and eel-like, and the stumpy little arms protrude towards the animal’s rear, rather than forward as they are even in T rex. Some have suggested the beast was semi-aquatic, although the emphasis has to be on the semi because there are no convincing features that suggest any significant adaptation to living in water.

Majungasaurus illustrated by Brett Booth

Darren Naish points out that the jaws look adapted to provide a wide gape, which is an aqueous adaptation in some fish and whales, but also in various land animals and birds. The use then is to burst something by pressure of the opening jaws when they have been pressed into a narrow space, birds that feed on grubs in rotten wood, for example, do it to break the wood and expose the grubs. Perhaps Majungasaurus was a scavenger that pushed its head and eel-like neck into carcases to consume their soft interiors, using their gapes to make space among the dead animal’s organs to be able to eat. So, they were a type of terrestrial vulture. Majungasaurus however is said to have had poor eyesight so it was not finding its food by vision, and most likely used smell. It stubby forelimbs pointing backwards allowed the animal to push itself further into the carcase, and perhaps the forelimbs could be used to help it extract itself having eaten its fill, or to grab a breath, by pushing forewards against the dead animal’s flesh!

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Convergence in RNA Solutions

28 January 2012, 2:10 am

Strong support for evolution—its fundamental machinery—came with the discovery by Watson and Crick of the double helical structure of the DNA (deoxyribonucleic acid) molecule. DNA is the blueprint of life. It contains in its sequences of nucleotides (nitrogen containing molecules able to form weak but specific bonds with each other) the factors or genes which influence variation and pass on characteristics from one generation to the next. The discovery that DNA was a double helix demonstrated in the most obvious way the basis for reproduction—the helix simply split down the center of its coil forming two separate halves. Each half then reformed the complete molecule from the surrounding nutrient molecules. Thus two complete molecules are formed from one and these can in turn divide and reform, multiplying the molecule as long as there are enough nutrient molecules remaining in the environment.

Astonishingly enough, experiments have been carried out showing that convergence can occur in the replication of molecules like these.

RNA (ribonucleic acid) is a fundamental molecule of life related in structure to DNA although simpler. It too is a replicating molecule. Sol Spiegelman extracted RNA from a virus and put it into a test tube with an enzyme (a molecule which helps a biochemical reaction to occur) and some nutrient molecules. The RNA replicated itself. A drop of the resulting liquid was extracted and put into another test tube containing only nutrient molecules and the enzyme. The drop contained some of the RNA molecules so these replicated as before. The same procedure was then repeated exhaustively. The RNA was analyzed at intervals to check its structure. It was found that the RNA evolved! Occasionally an error in the replication process occurred to yield a slightly different RNA molecule. If that proved not to be as good at replicating as the rest of them then it soon got diluted to such an extent that the drop extracted from the last test tube contained none of the mutant molecules and that “species” had died out. If however the mutant was better at reproducing itself in the test tube environment than its parent, the converse occurred. Before long the original RNA had become so diluted by the mutant’s offspring that the drop taken from the last test tube contained none of the original and the mutant RNA had survived the extinction of the old “species”. After many trials a stable species seemed to evolve—the one best suited to the test tube world in which it lived!

Remarkably, the experimenters went on to provide the most spectacular example of convergence. They found that the same RNA molecule evolved from different RNA taken from different sources!

The story is yet more amazing. Manfred Eigen, a Nobel prizewinning chemist, carried out a complementary and even more unlikely experiment. He used no RNA as a “seed” molecule. He just used the enzyme and the nutrient molecular broth. After many trials he found that RNA built itself spontaneously from the nucleotides and other molecules present. It then evolved into essentially the same test tube “species” as before. Its size and general structure were the same but there were some minor variations. Just as you would expect of convergence from considerably different starting points.

Originally posted 2009-06-10 01:05:53. Republished by Blog Post Promoter

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Lucy Walked Like a Modern Human

21 January 2012, 1:18 am
Afarensis metatarsal bone

Some paleoanthropologists think Australopithecus afarensis walked like modern humans and others thought it walked more like a chimpanzee. Walking like a human requires straighter legs and a particular type of foot, different from that of chimpanzees which are able to grip branches with their feet. PhysOrg reports that a fossilized foot bone recovered from Hadar, Ethiopia, described in a report by Carol Ward of the University of Missouri, William Kimbel and Donald Johanson, both of Arizona State University (ASU)’s Institute of Human Origins, shows that by 3.2 million years ago human ancestors walked bipedally with a modern human like foot. The fossil, a fourth metatarsal, or midfoot bone, indicates that a permanently arched foot was present in the species Australopithecus afarensis.

Understanding that the foot arches appeared very early in our evolution shows that the unique structure of our feet is fundamental to human locomotion. If we can understand what we were designed to do and how natural selection shaped the human skeleton, we can gain insight into how our skeletons work today. Arches in our feet were just as important for our ancestors as they are for us.
Carol Ward

Humans, uniquely among primates, have two arches in their feet, longitudinal and transverse, which are composed of the midfoot bones and supported by muscles in the sole of the foot. During bipedal locomotion, these arches perform two critical functions: leverage when the foot pushes off the ground and shock absorption when the sole of the foot meets the ground at the completion of the stride. Ape feet lack permanent arches, are more flexible than human feet and have a highly mobile large toe, important attributes for climbing and grasping in the trees. None of these apelike features are present in the foot of A afarensis.

This fourth metatarsal is the only one known of A afarensis and is a key piece of evidence for the early evolution of the uniquely human way of walking. The ongoing work at Hadar is producing rare parts of the skeleton that are absolutely critical for understanding how our species evolved.
William Kimbel

So, the human foot has arches and a complete foot skeleton is not needed to show them. The fourth metatarsal of the A afarensis foot recovered from Hadar, strongly suggests arches and so a human style of walking. The specimen was recovered from the richest source of A afarensis fossils in eastern Africa, with more than 250 specimens, representing at least 17 individuals, so far known. This species, whose best known specimen is Lucy, discovered by Don Johanson, lived in eastern Africa about 3 million years ago.

Before A afarensis, the species A anamensis lived in Kenya and Ethiopia from 4.2 to 4.0 million years ago, but its skeleton is not well known. At 4.4 million years ago, Ethiopia’s Ardipithecus ramidus is the earliest human ancestor well represented by skeletal remains. Although Ardipithecus appears to have been partly terrestrial biped, its foot retained many features of tree dwelling primates, including a divergent, mobile first toe. The foot of A afarensis, as with other parts of its skeleton, is much more like that of living humans, implying that by the time of Lucy, our ancestors no longer depended on the trees for refuge or resources.

The Hadar project is the longest running paleoanthropology field program in the Ethiopian rift valley, now spanning more than 38 years. Since 1973, the fieldwork at Hadar has produced more than 370 fossil specimens of A afarensis between 3.4 and 3.0 million years ago—one of the largest collections of a single fossil hominin species in Africa—as well as one of the earliest known fossils of Homo and abundant Oldowan stone tools (about 2.3 million).

Through ASU’s Institute of Human Origins, the Hadar project plays an important role in training Ethiopian scholars by offering graduate degree and postdoctoral opportunities in the US Promotion of local awareness of the global scientific importance and Ethiopian cultural heritage value of the Hadar site is also a project priority. Additionally, the fundraising phase of a planned “Hadar Interpretive Center” at Eloaha town, 30 kilometers from the site, was successfully completed in January 2011.

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The Dinosauroid: A Humanoid Dinosaur

14 January 2012, 12:29 am

Dale Russell, discoverer of Stenonychosaurus (now called Troodon), then of the National Museum of Natural Sciences in Ottawa, Canada, postulated that late Cretaceous dinosaurs were well on the way to becoming intellectual animals, and would have succeeded if the dinosaurs had not suffered extinction. Stenonychosaurus had an opposable thumb, stood upright about three feet tall and had binocular vision. Russell commented:

It had all the ingredients of success that we see later in the development of the apes.

The Troodon and the Dinosauroid

The Troodon and the Dinosauroid

He believes that Stenonychosaurs were the “chief predators on Cretaceous mammals” and that there must have been quite a lot of them because, by the end of the Cretaceous, there were a lot of mammals, though they were small. These dinosaurs were obviously outwitting mammals, if Russell is right, and he thought evolution would have led them to have become intelligent Dinosaurs—Dinosauroids!

Jeff Hecht, a Massachusetts, USA, science and technology writer explained in issue 15 of Cosmos, June 2007 that Dale Russell’s idea of the dinosauroid began as a thought experiment. Scientists were beginning to realize dinosaurs were not as slow witted as reptiles, as they had supposed since Victorian times. Measurements of fossil dinosaurs showed steady increases in the encephalisation quotient (EQ) over millions of years. The EQ is a relative measure of an animal’s brain weight compared to that of an average animal of a related species and the same body weight. An EQ of 2.0 means the animal has a brain twice the weight of similar animals with the same weight. Russell wondered how the trend might have affected non avian dinosaurs had they survived to the present day. Could they have become intelligent, like us? Research has revealed intelligent behaviour in birds, as we now know, the closest living relatives of dinosaurs.

Hecht says we tend to think intelligence is a good thing that contributed to the evolutionary success of our species. So, what’s good for humans should have been good for dinosaurs. Yet some palaeontologists echo the late US evolutionary biologist Stephen Jay Gould, who doubted natural selection has any inherent preference for what we call intelligence. It would hardly be surprising as evolution is said not have any preferences at all because its direction depends upon the conditions pertaining at some particular time, and the characteristics of the animal itself. These can change from era to era. That said the overall tendency is for growth in brain size (Marsh’s law) and it is intelligence that need larger brains. Moreover, species seem to have developed characteristics that allow rapid evolution when it is needed, and that can give evolution direction!

Russell’s starting point was a fast, 60 kg, two legged predator called Troodon (Troodon formosus), which lived about 75 million years ago in Canada. The first Troodon skull showed that its brain, relative to its body size, was large for a dinosaur. Russell calculated that Troodon had an EQ that was nearly six times larger than the average of known dinosaurs, though small compared to modern humans. He extrapolated the figures to show that, if Troodon had survived and retained the same body size, its modern day descendants could have a brain volume of 1,100 cm3—comparable to that of some modern humans. Moreover, the placement of Troodon’s large eyes suggested it had binocular vision, and the outer two of its three fingers also appear to be opposable.

Russell decided that evolving a big brain would have reshaped the original dinosaur, and it is this reshaping that made it humanoid, and thus a dinosauroid. The back of its skull would have expanded to house the enlarged, bird shaped brain. The snout would have shrunk and the teeth would have disappeared, leaving a short, turtle like beak. To support the heavy head, Russell replaced the dinosaur’s long, horizontal neck with a short, upright one. That, in turn, required an upright posture, which would have made plausible the use of tools and weapons. As the body became upright, he expected the tail to diminish until it disappeared, as it did with our great ape relatives, but that the dinosauroid would retain reptilian traits of scaly skin and the lack of external genitals, and to have evolved live birth for its large headed young.

Russell’s colleague, Ron Sequin, sculpted a 1.3 metre tall dinosauroid for display beside a life sized model of Troodon. But it was, remember, a thought experiment, a serious conjecture based on careful scientific study, but it was not a testable scientific hypothesis, nor was it meant to be. Curious then that many people seem to have assumed it was, and dismiss Russell as some sort of nut!

Such criticisms are unwarranted and unfair. The speculation was sound and sensible. A testable hypothesis is that the dinosauroid actually did evolve, and destroyed itself in the KT extinction event. It was the Anthroposaurus sapiens!

Originally posted 2010-04-12 17:06:57. Republished by Blog Post Promoter

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Dinosaurs Cold-Blooded?

6 January 2012, 10:50 pm
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Besides human ego, there was another obstacle to the idea of intelligence in dinosaurs. Dinosaurs were believed to be cold-blooded—they were reptiles—reptiles and lizards are cold-blooded. Warm-blood seems necessary for a high capacity brain. Today there is no such objection to the evolution of intelligence in the dinosaurs—they were warm-blooded! They were not cold-blooded and sluggish reptiles—they were not reptiles. And they were active, not sluggish.

Given warm-blooded animals, intelligence could have evolved repeatedly—a conclusion directly contradicting Gould’s. On passing a certain threshold, intelligence could evolve increasingly rapidly. If the dinosaurs reached the threshold, they could have become intelligent in a geologically short time. Using human evolution as our only example, we can estimate the timescale using the molecular clock.

The molecular clock depends upon natural selection being neutral towards most genes. A beneficial gene survives in a population, but so does a gene that has no particular affect for good or ill. Only genes which confer manifestly disadvantageous characteristics die out through natural selection. Genes continually mutate at a fairly constant rate and, providing that the mutant genes are not harmful, they will spread among a population in which interbreeding freely occurs. Each species therefore has a common gene pool. Once species have separated, their genes no longer mix, there is no longer a common gene pool. If a mutant gene now arises in an animal of one species, it will spread among that species but it cannot spread into the other. The longer the time since two species separated, the greater the difference in genetic and protein structure. Comparing genetic and protein differences between species, and knowing the rate at which the differences multiply, allows us to calculate when speciation occurred.

In 1967, using a molecular dating technique, Victor Sarich and Allan Wilson showed that man diverged from the African apes as little as five million years ago. For orthodox paleontologists this was far too short a time. It spoilt their theories and put us too close for the good of their egos to the apes. They abused Sarich and Wilson and ignored their results for years. Gribbon and Cherfas say it was “as if theoretical astronomers had ignored the discovery of pulsars”. Yet, only a few million years ago, our ancestors were the creatures from which also descended present day chimpanzees. From that time, a line branched off the common stock that became human. Mankind apparently reached the threshold of intelligence within perhaps the last five million years.

Sixty of the sixty five million years of domination of the earth by mammals elapsed before the intelligent model went into the prototype stage, but then in only about five million years technological society evolved. Sixty million years of mammalian evolution to arrive at the threshold of intelligence, yet the dinosaurs had 140 million years at the top—twice as long as the mammals. Could animals that succeeded so well for so long fail to develop an intelligent version of their own? There must be a possibility that dinosaurs too achieved thinking status… but 65 million years before us.

If intelligent dinosaurs existed, they must have made a big impression on their world, just as we have. Where then are their ruins, their relics and their kitchen middens?

Consider the following questions. Out of about 12 billion human people that have ever lived on the earth, how many have left any mark? What remains of their accumulated experience? Out of an estimated 80 million species of living organisms on the earth today how many will be classified before they become extinct? How many will leave any fossil remains? How many of the millions of insect species? How many of the estimated 8600 birds? How many of the 4000 mammals? Hardly any! Most living things, intelligent or otherwise do not leave a trace. Species that are constructed mainly of soft tissues which decay quickly effectively leave no fossils. Species that live in environments unconducive to fossilization leave few fossils. Species that evolve and die off quickly leave few remains. Technological civilization only began two hundred years ago and might end in the next hundred. Human civilization, hugely impressive to us, is only an oily smear in the geological record.

In the millions of years that the dinosaurs dominated the earth, thousands of dinosaur species, billions of individuals, have left no trace. If just one of those species came to prominence very rapidly in evolutionary terms, as mankind has, perhaps making no significant mark until its last few centuries, would much be seen in the rocks 65 million years later? I think not, even if anyone were looking for signs of intelligence. And who’s looking? Not the paleontologists!

Experts, though they defend their own dogmas as determinedly as any medieval prelate, are liable to regard unorthodox ideas with contempt and show little eagerness to investigate them. These experts are often wrong. Though they are technically good at determining facts, they are prone to ignore troublesome ones, and continue to market outmoded theories until well beyond their sell-by date. Worse still, some are inclined to assert whatever is most acceptable to their peers or their paymasters. It pays to be skeptical about such people and wary of their assertions.

Independent writers and researchers in the last couple of decades have put together sufficient to challenge the paleontological dogmatists. Unorthodox proposals deserve attention if only to provoke the experts to justify their conventional arguments and thus periodically to force them into an honest reappraisal. Admittedly, these views are speculative, and experts like to speak authoritatively even when they have not themselves seen fit to actually examine the evidence. They disdain speculation—though one of Britain’s leading thinkers, Richard Dawkins, allows that careful selective speculation can be constructive, and every hypothesis is necessarily speculative.

Particularly speculative hypotheses face a contradiction—they need more proof than less controversial ones, yet often the absence of convincing evidence is the reason why speculation is necessary. That is true here—direct evidence is sparse and badly documented. Indirect or circumstantial evidence is more plentiful, is generally sound, and constitutes the greater part of this argument. And speculations might stimulate a more open-minded look at past events. Anomalies in old rock strata might be taken seriously and accurately dated rather than ignored when there is a speculative hypothesis that could explain them. Curious artifacts and impressions in very ancient rocks, of the Cretaceous Period particularly, might be studied systematically to see whether an adequate theory can be constructed to explain them.

More importantly, we should examine the parallels between the present time and mass extinctions of the Cretaceous. Tens of millions of years hence, geologists will simply see a sudden reduction in diversity terminating the Tertiary epoch. Will they notice that a couple of inches of sediment contain traces of one species of ape which briefly exploded in numbers prior to the mass extinction? It is doubtful.

Is the mass extinction of species the only legacy we wish to leave, as our sapient dinosaurian antecedents did? If this probe into time’s secrets motivates enough people to disown our dinosaur heritage and to stop our assault on the planet, we might yet—unlike the dinosaurs—survive.

Originally posted 2010-04-12 18:01:55. Republished by Blog Post Promoter

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Homo Sapiens Has a Better Sense of Smell than Related Hominins

1 January 2012, 10:49 pm

Scientists, led by Markus Bastir and Antonio Rosas of the Spanish Natural Science Museum (CSIC) and including Chris Stringer and Robert Kruszynski at the Natural History Museum, have found that areas of the brain, the temporal lobes that correspond to cognition (language, memory and social function) and the olfactory bulbs that correspond to sense of smell, are larger in Homo sapiens compared with other human species. They are about 12 percent larger than those of Neanderthals, Homo neanderthalensis. It suggests our sense of smell may have been as important as language in helping to give us, modern humans, an evolutionary advantage over other human relatives such as the Neanderthals. The two areas work together and are more important in the evolution of the modern human brain than previously thought.

The team analysed fossil skulls of hominins—ancient human relatives—including Homo sapiens, Homo neanderthalensis and Homo erectus. They used a new and very precise way to measure and compare the volumes of areas inside hominin skulls dating up to nearly 2 million years ago, and produced 3D models that helped reveal the detail of their internal structures. Kruszynski said:

Those of Homo sapiens—our own species—showed a surprising change of internal architecture compared with their predecessors, in the area housing the olfactory and temporal regions. Such changes were not so evident in the Neanderthal skulls that were studied. The different evolutionary pathways that these two species took may be part of the process that led to the distinct patterns found in Homo neanderthalensis and Homo sapiens.

Neandertal Nose

Until now, sense of smell has been thought of as less significant for humans compared to our other senses. Stringer explains:

It has been traditional to believe that we have reduced olfactory (smell) senses compared with other primates, and by implication, earlier humans. However, the data in this study suggest the opposite—that modern humans actually have an enhanced sense of smell. This might be because of the greater range of environments in which we live and the greater range of foods modern humans exploit, and/or an increased social role for olfaction in our more complex social interactions.

Smells are processed in the same brain regions responsible for processing emotion, motivation, fear, memory, pleasure and attraction, making them an important aspect of social interactions. And olfaction is among the oldest senses in vertebrates, the only one that establishes a direct connection between the brain and its environment, Bastir says.

The links between cognition and olfaction have caused neuroscientists to use the term “higher olfactory functions” to describe those brain functions that combine the two. The team says that the larger olfactory bulbs and temporal lobes of Homo sapiens would have made evolutionary sense in a social context. They would have contributed to kinship recognition, enhanced family relations, group cohesion and social learning, all crucial factors that scientists believe allowed modern humans to progress and become the only surviving human species.

Yet if smell is so important to social function, many more social primates should have benefitted at earlier dates. The sense of smell has been thought to have been fading in humans because it does not serve many of the functions it once did socially and in feeding, as human abilities to get adequate food supplies improved. It is an interesting finding, but will need a lot of confirmatory work and evidence.

Of course, if humans evolved via an aquatic phase the sense of smell might have atrophied, before new uses were found for it when we emerged from the water. We have speculated about an incest gene. Smell might have been particularly important for the incestuous mutants to recognize each other. That could be a strong reason for the observations. What then would be the consequences today?

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Dromaeosaurs Killed Prey Like Modern Raptors and thereby Developed Flight

1 January 2012, 9:45 pm

Denver W Fowler, Elizabeth A Freedman, John B Scannella and Robert E Kambic of Montana State University’s Museum of the Rockies have revealed how dromaeosaurid dinosaurs like Velociraptor and Deinonychus used their sickle claws. It suggests a new hypothesis on the evolution of flight.

Dromaeosaurids are fairly small predatory dinosaurs closely related to birds, famous for having an enlarged sickle claw on digit two (inside toe) of the foot. The sickle claw was once thought to have been a ripping weapon, to slash victims to death. Now it is compared to how modern raptors behave. Fowler explained:

Modern hawks and eagles possess a similar enlarged claw on their digit 2’s, something that hadn’t been noted before we published on it back in 2009. We showed that the enlarged D-2 claws are used as anchors, latching into the prey, preventing their escape. We interpret the sickle claw of dromaeosaurids as having evolved to do the same thing—latching in, and holding on.

This strategy is only really needed for prey that are about the same size as the predator; large enough that they might struggle and escape from the feet. Smaller prey are just squeezed to death, but with large prey all the predator can do is hold on and stop it from escaping, then basically just eat it alive. Dromaeosaurs lack any obvious adaptations for dispatching their victims, so just like hawks and eagles, they probably ate their prey alive too.

Dinosaurs adapted for running or walking have a foot proportioned like a modern emu, with a large middle toe, and side toes that are shorter and about equal in length (Gallimimus, left, Allosaurus, middle). Deinonychus (right) is different, with an unusually long outer toe (D-4), and very short inner toe (D-2), proportions suited to grasping. (Image by Denver Fowler).

Other features of bird of prey feet gave clues as to the functional anatomy of their ancient relatives; toe proportions of dromaeosaurids seemed more suited for grasping than running, and the metatarsals—bones between the ankles and the toes—are more adapted for strength than speed. Fowler thinks that this indicates that Velociraptor and its kin were adapted for a strategy other than simply running after prey:

Unlike humans, most dinosaurs and birds only walk on their toes, so the metatarsus forms part of the leg itself. A long metatarsus lets you take bigger strides to run faster; but in dromaeosaurids, the metatarsus is very short, which is odd. When we look at modern birds of prey, a relatively short metatarsus is one feature that gives the bird additional strength in its feet. Velociraptor and Deinonychus also have a very short, stout metatarsus, suggesting that they had great strength but wouldn’t have been very fast runners.

Deinonychus foot grasping. (Image by Denver Fowler).

The ecological implications become especially interesting when dromaeosaurids are contrasted with their closest relatives—a similar group of small carnivorous dinosaurs called troodontids. Troodontids and dromaeosaurids started out looking very similar, but over about 60 million years they evolved in opposite directions, adapting to different niches. Dromaeosaurids evolved towards stronger, slower feet, suggesting a stealthy ambush predatory strategy, adapted for relatively large prey. By contrast, troodontids evolved a longer metatarsus for speed and a more precise, but weaker grip, suggesting they were swift but probably took relatively smaller prey.

The study also has implications for the next closest relatives of troodontids and dromaeosaurids, birds. An important step in the origin of modern birds was the evolution of the perching foot. A grasping foot is present in the closest relatives of birds, but also in the earliest birds like Archaeopteryx. Fowler said:

We suggest that this originally evolved for predation, but would also have been available for use in perching. This is what we call “exaptation”, a structure evolved originally for one purpose that can later be appropriated for a different use. The same mechanism may be responsible for the evolution of flight.

When a modern hawk has latched its enlarged claws into its prey, it can no longer use the feet for stabilization and positioning. Instead the predator flaps its wings so that the prey stays underneath its feet, where it can be pinned down by the predator’s bodyweight. The predator’s flapping just maintains its position, and does not need to be as powerful or vigorous as full flight would require. Get on top, stay on top. It’s not trying to fly away. We see fully formed wings in exquisitely preserved dromaeosaurid fossils, and from biomechanical studies we can show that they were also able to perform a rudimentary flapping stroke. Most researchers think that they weren’t powerful enough to fly. We propose that the less demanding stability flapping would be a viable use for such a wing, and this behavior would be consistent with the unusual adaptations of the feet.

The sickle claw of dromaeosaurids evolved for grasping prey. Dromaeosaurids lacked physical structures for quick dispatch of prey, so probably ate their victims alive. (Lower right drawing by Lee Hall, others by Nate Carroll). The researchers suggest that this ’stability flapping’ uses less energy than flight, making it an intermediate flapping behavior that may be key to understanding how flight evolved.

Others also propose that understanding flapping behaviors is key to understanding the evolution of flight.

If we look at modern birds, we see flapping being used for all sorts of behaviors outside of flight. In our paper, we are formally proposing the “flapping first” model, whereby flapping evolved for other behaviors first, and was only later exapted for flight by birds.

The researchers believe their new ideas will open multiple new lines of investigation into dinosaur paleobiology, and the evolution of novel anatomical structures. Fowler said:

We’re looking at old paleontological questions with a fresh perspective, taking a different angle. Just as you have to get beyond the idea that feet are used just for walking, so we are coming to realize that many unusual structures in modern animals originally evolved for quite different purposes. Revealing the selection pathways that mold and produce these structures helps us to better understand the major evolutionary transitions that shaped life on this planet.

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