Natural Selection is one of the main concepts found within the theory of evolution. It was discovered by Charles Darwin and Alfred Russel Wallace though Darwin championed the idea in his book “On the Origin of Species”.
Natural selection can be defined as the process by which random evolutionary changes are selected for by nature in a consistent, orderly, non-random way.
When coupled with descent with modification, Natural Selection can cause a population to evolve for fitness within a given environment over multiple generations.
Natural Selection is an observable fact. By carefully observing populations of living things with short life cycles you can actually watch it happen.
Want to learn more? Check out our notes for this video. Included are links to three examples of natural selection witnessed by researchers. There are many more as well.
Posts tagged Genetics.
What Cannibals Could Teach Us About Evolution
Three recent studies provide a glimpse into nature’s most gruesome diet—and what it reveals about evolution.
In the past few decades, scientists studying the eating habits of Earth’s creatures have noticed something strange: the babies of several species, from tiger sand sharks to fruit flies, are eating each other.
Yikes.
Biologist Maps the Family Tree of All Known Snake and Lizard Groups
May 8, 2013 — A George Washington University biologist and a team of researchers have created the first large-scale evolutionary family tree for every snake and lizard around the globe.
Handedness in Neandertals from the El Sidrón (Asturias, Spain): Evidence from Instrumental Striations with Ontogenetic Inferences
The developed cognitive capabilities for Homo sapiens seems to be the result of a specialized and lateralized brain, and as a result of this, humans display the highest degree of manual specialization or handedness among the primates. Studies regarding its emergence and distribution within the genus Homo show that handedness is present very early. The mode in which it was articulated and spread across the different species during the course of human evolution could provide information about our own cognitive capacities. Here we report the manual laterality attributed to eleven 49,000 old Neandertal individuals from El Sidrón cave (Spain), through the study of instrumental or cultural striations on the anterior dentition. Our results show a predominant pattern addressed to right-handers. These results fit within the modern human handedness distribution pattern and provide indirect evidence for behavior and brain lateralization on Neandertals. They support the early establishment of handedness in our genus. Moreover, the individual identified as Juvenile 1 (6–8 years old at death), displays the same striation pattern as the adult Neandertals from the sample, and thereby the ontogenic development of manual laterality in that Neandertal population seems to be similar to that of living modern humans” (read more/open access).
(Open access source: PLoS ONE 8(5): e62797)
Why we need to dispel the notion of dualistic free will ›
I’ve always argued that philosophers spend way too much time trying to limn conceptions of free will that avoid dualism. Instead, they write books confecting compatibilism. I regard this exercise as largely a waste of time. If philosophers truly intend for their lucubrations to change the world, then I’d think that they’d spend more of their time spreading the word about our growing knowledge of how behavior is determined and less on trying to show how we have some kind of free will.
An excellent article on an emerging field known as neurocriminology. From the article:
The field of neurocriminology—using neuroscience to understand and prevent crime—is revolutionizing our understanding of what drives “bad” behavior. More than 100 studies of twins and adopted children have confirmed that about half of the variance in aggressive and antisocial behavior can be attributed to genetics. Other research has begun to pinpoint which specific genes promote such behavior.
Brain-imaging techniques are identifying physical deformations and functional abnormalities that predispose some individuals to violence. In one recent study, brain scans correctly predicted which inmates in a New Mexico prison were most likely to commit another crime after release. Nor is the story exclusively genetic: A poor environment can change the early brain and make for antisocial behavior later in life.
Turtle Genome Analysis Sheds Light On Turtle Ancestry and Shell Evolution
Apr. 28, 2013 — From which ancestors have turtles evolved? How did they get their shell? New data provided by the Joint International Turtle Genome Consortium, led by researchers from RIKEN in Japan, BGI in China, and the Wellcome Trust Sanger Institute in the UK provides evidence that turtles are not primitive reptiles but belong to a sister group of birds and crocodiles. The work also sheds light on the evolution of the turtle’s intriguing morphology and reveals that the turtle’s shell evolved by recruiting genetic information encoding for the limbs.
Admixture and Assimilation in Central Europe
- by JCM Ahern, I Janković, J-L Voisin and FH Smith
Selected images from presentation given at The Second Front Range Neandertal Workshop, 23 February, 2013 (University of Wyoming, Department of Anthropology). Click through for link to full presentation.
Fish’s DNA May Explain How Fins Turned to Feet
In the hope of reconstructing a pivotal step in evolution — the colonization of land by fish that learned to walk and breathe air — researchers have decoded the genome of the coelacanth, a prehistoric-looking fish whose form closely resembles those seen in the fossils of 400 million years ago.
2. Concordance between “folk” and “scientific” species. Scientific facts ultimately derive from the agreement of independent observers. One can apply this principle to the problem of species reality by determining whether different observers—particularly those not sharing obvious biases—see the same divisions in nature. Biologists and anthropologists alike have conducted these studies. Typically, they survey a region’s indigenous people, who lack formal biological training, and ask them to list the types of animals or plants in their habitat. These groupings of organisms into ‘folk species’ can then be compared to the ‘Linnaean species’ recognized by modern taxonomists.
Such comparisons can yield three possible results. First, there can be one-to-one correspondence between Linnaean and folk species, which is strong evidence that nature is partitioned into units consistently recognized by people of different backgrounds. Second, a folk species can be undifferentiated, meaning that it includes two or more Linnaean species. Such a result might be considered evidence for the reality of species if the Linnaean species are very similar to each other, differing in traits cryptic to nonscientists. Finally, folk species can be overdifferentiated, with a Linnaean species in one area being described as two or more folk species. Consistent overdifferentiation would constitute evidence against the reality of species.
The results of these studies are consistent: there is a remarkable coincidence between folk species and Linnaean species. Moreover, of the exceptions that do exist, most involve under- rather than overdifferentiation. The first compelling evidence was Mayr’s (1963) observation that tribesman of the Arfak Mountains of New Guinea had 136 vernacular names for the 137 Linnaean species of birds they encountered. In a more thorough analysis, Diamond (1966) studied bird names used by the Fore people of New Guinea. Their habitat contained 120 Linnaean species, with roughly 80% of these showing a one-to-one correspondence with Fore names. Diamond notes (1966, p. 1103):
To a zoologist, the ability of the Fore to distinguish between closely similar species is impressive…[In two species of warblers] the differences are sufficiently subtle that I was often in doubt about the identity of the species held in the hand. Nevertheless the Fore not only had different names for the two birds…but also could identify them correctly in the field at moderate distances without binoculars. In this case small differences in behavior and call-note had probably alerted them to the fact that more than one kind of bird was present.
Diamond also took a group of Fore to lower elevations and asked them to give names to bird species they had never encountered. Ninety percent of the 103 Linnaean species were recognized as distinct folk species. Diamond argues, ‘That the elements in these two dissimilar classificatory systems nevertheless usually show a one-to-one correspondence strikingly illustrates the objective reality of the species” (1966, p. 1104).
Regardless of the group surveyed, then, there is a very strong, although not perfect, correspondence between folk and Linnaean species—a correspondence of around 70%. Given the subtle traits used to designate Linnaean species (which can cause underdifferentiation of folk names) and the geographic variation of some species, there can be no reasonable expectation of perfect correspondence. Strikingly, one sees few cases of overdifferentiation. These results strongly support the view that people of different backgrounds recognize similar units of natural diversity. This buttresses the claim that species are real.
Majnep and Bulmer (1977) obtained similar results studying animals encountered by the Kalam people of New Guinea. Of 176 bird species recognized by Western zoologists, 123 had a one-to-one correspondence with the folk designation, while there were 24 cases of underdifferentiation. This yields a 70-80% correspondence between names. The concordance between Kalam and Linnaean species is about 80% for frogs and 95% for reptiles (Bulmer and Tyler 1968; Bulmer et al. 1975).
In view of the common claim that species are less ‘real’ in plants than in animals, one might expect to find less correspondence between Linnaean and folk species in plants. However, the work of Berlin et al. (1974) among the Tzeltal of southern Mexico shows that this expectation is incorrect. The Tzeltal have 471 folk names for plants growing in their area; of these, 66% are identical to Linnaean species. (Some of the plants surveyed are not sympatric, and geographic variation within Linnaean species may have reduced this correspondence.)
Regardless of the group surveyed, then, there is a very strong, although not perfect, correspondence between folk and Linnaean species—a correspondence of around 70%. Given the subtle traits used to designate Linnaean species (which can cause underdifferentiation of folk names) and the geographic variation of some species, there can be no reasonable expectation of perfect correspondence. Strikingly, one sees few cases of overdifferentiation. These results strongly support the view that people of different backgrounds recognize similar units of natural diversity. This buttresses the claim that species are real.
It must be admitted that not everyone finds this evidence convincing. Ridley (1966, p.421) notes, ‘[T]he fact that independently observing humans see much the same species in nature does not show that species are real rather than nominal categories. The most it shows is that all human brains are wired up with a similar perceptual cluster statistic.’ (See also Mishler and Donoghue 1982, p. 493.)
These views can be interpreted in two ways. The weaker claim is that humans have an evolved tendency to subdivide and categorize, even when presented with a continuum. Yet this hypothesis does not explain why, if species are not discrete, people of widely diverse backgrounds—geographical, cultural, and scientific—tend to recognize the same groups. Proponents of the view that species are illusory must then make the stronger claim that human neurological wiring somehow constrains us to divide continua at the same boundaries. They might argue, for instance, that the three types of cones in the human eye—with differential sensitivities to blue, red, and green light—cause all humans to divide the continuous spectrum of light into a largely identical set of colors. Indeed, as different societies incorporate colors into their vocabulary, the six ‘primary constituent colors’ are added in a nearly identical sequence (Durham 1991).
However, while the ‘neurological wiring’ argument might conceivably explain congruent divisions of single traits, the claim loses force when dealing with groups of traits. We must remember that the congruence of species names between folk and Western taxonomy reflects the assessment of multiple traits. And there is no reason why our neurological wiring for recognizing, say, size, would divide up a biological continuum into the same groups as would our wiring for shape, for color, and so on. Moreover, using one set of traits yields clusters identical to those recognized using a different set of traits. It is well known, for example, that morphological discontinuities almost always coincide with genetic discontinuities in DNA sequences. This consistent carving of nature at the same joints is a powerful argument for the reality of species.
One can make a related argument based not on humans but on other species. In animals, individuals recognize conspecifics but not heterospecifics during the breeding season—the same differences recognized by humans. A male robin courts only female robins, not birds that humans consider members of other species. Pollinator-specific insects also discriminate between plant species recognized as different by humans. Likewise, many host-specific herbivores and parasites are good ‘taxonomists,’ recognizing the same species as do biologists . Even if one accepts that all human brains are wired with the same ‘perceptual cluster statistic,’ it hardly seems reasonable to assume that this statistic is identical in other animals.
Something’s Fishy in the Tree of Life: Largests and Most Comprehensive Studies of Fish Phylogeny
Apr. 19, 2013 — Fishes account for over half of vertebrate species, but while groups such as mammals, birds and reptiles have been fairly well understood by scientists for decades, knowledge about relationships among many types of fishes was essentially unknown — until now.
The Deconversion Movement
- Roger Martin
