Before the scientific era, people often made up imaginative stories to explain what they saw in the world. The scientific method changed that by requiring rigorous experimentation to test hypotheses and determine what is real.
General overview The evidence for evolution Darwin and other 19th-century biologists found compelling evidence for biological evolution in the comparative study of living organisms, in their geographic distribution, and in the fossil remains of extinct organisms.
The amount of information about evolutionary history stored in the DNA and proteins of living things is virtually unlimited; scientists can reconstruct any detail of the evolutionary history of life by investing sufficient time and laboratory resources.
The following sections identify the most productive of these sources and illustrate the types of information they have provided. The fossil record Paleontologists have recovered and studied the fossil remains of many thousands of organisms that lived in the past. This fossil record shows that many kinds of extinct organisms were very different in form from any now living.
It also shows successions of organisms through time see faunal succession, law of ; geochronology: Determining the relationships of fossils with rock stratamanifesting their transition from one form to another. When an organism dies, it is usually destroyed by other forms of life and by weathering processes.
On rare occasions some body parts—particularly hard ones such as shells, teeth, or bones—are preserved by being buried in mud or protected in some other way from predators and weather.
Eventually, they may become petrified and preserved indefinitely with the rocks in which they are embedded.
Methods such as radiometric dating The evolution and spread of scientific the amounts of natural radioactive atoms that remain in certain minerals to determine the elapsed time since they were constituted—make it possible to estimate the time period when the rocks, and the fossils associated with them, were formed.
Radiometric dating indicates that Earth was formed about 4. The earliest fossils resemble microorganisms such as bacteria and cyanobacteria blue-green algae ; the oldest of these fossils appear in rocks 3.
The oldest known animal fossils, about million years old, come from the so-called Ediacara faunasmall wormlike creatures with soft bodies. Numerous fossils belonging to many living phyla and exhibiting mineralized skeletons appear in rocks about million years old.
These organisms are different from organisms living now and from those living at intervening times. Some are so radically different that paleontologists have created new phyla in order to classify them. The first vertebrate s, animals with backbones, appeared about million years ago; the first mammal s, less than million years ago.
The history of life recorded by fossils presents compelling evidence of evolution. The fossil record is incomplete. Of the small proportion of organisms preserved as fossils, only a tiny fraction have been recovered and studied by paleontologists.
In some cases the succession of forms over time has been reconstructed in detail. One example is the evolution of the horse. The horse can be traced to an animal the size of a dog having several toes on each foot and teeth appropriate for browsing; this animal, called the dawn horse genus Hyracotheriumlived more than 50 million years ago.
The most recent form, the modern horse Equusis much larger in size, is one-toed, and has teeth appropriate for grazing. The transitional forms are well preserved as fossils, as are many other kinds of extinct horses that evolved in different directions and left no living descendants.
Numbered bones in the forefoot illustrations trace the gradual transition from a four-toed to a one-toed animal. Using recovered fossils, paleontologists have reconstructed examples of radical evolutionary transitions in form and function. For example, the lower jaw of reptiles contains several bones, but that of mammals only one.
The other bones in the reptile jaw unmistakably evolved into bones now found in the mammalian ear. At first, such a transition would seem unlikely—it is hard to imagine what function such bones could have had during their intermediate stages.
Yet paleontologists discovered two transitional forms of mammal-like reptiles, called therapsid s, that had a double jaw joint i.
Many people think evolution requires thousands or millions of years, but biologists know it can happen fast. it must spread through a population. Every person carries two copies of each gene. 7 Department of Biochemistry and Molecular Biology, Bio21 Molecular Science and Biotechnology Institute, (WGS), we have been able to make substantive advances in understanding the dynamics of AMR evolution and spread in bacterial populations. WGS has become the key technology for understanding pathogen evolution, population dynamics. Methods for differentiating pathogen isolates are essential for understanding their evolution and spread, as well as for the formulation of effective clinical strategies. Current typing methods for bacterial pathogens focus on a limited set of characteristics providing data with limited resolving power. Harris et al. (p. ) used a high-throughput genome sequencing approach to show that.
Not one but many creatures intermediate between living apes and humans have since been found as fossils. The oldest known fossil hominin s—i.
Ardipithecus lived about 4. Numerous fossil remains from diverse African origins are known of Australopithecusa hominin that appeared between 3 million and 4 million years ago. Australopithecus had an upright human stance but a cranial capacity of less than cc equivalent to a brain weight of about gramscomparable to that of a gorilla or a chimpanzee and about one-third that of humans.
Its head displayed a mixture of ape and human characteristics—a low forehead and a long, apelike face but with teeth proportioned like those of humans. Other early hominins partly contemporaneous with Australopithecus include Kenyanthropus and Paranthropus; both had comparatively small brains, although some species of Paranthropus had larger bodies.
Paranthropus represents a side branch in the hominin lineage that became extinct. Along with increased cranial capacity, other human characteristics have been found in Homo habiliswhich lived about 1.The Evolution of a Scientific American Graphic: Cosmic Hunt.
(See his Scientific American article “Scientists Trace Society’s Myths to even if not used in the final spread, became. Scientific American is the essential guide to the most awe-inspiring advances in science and technology, The Evolution of Prejudice.
Evolution. Ritual Sacrifice May Have Shaped Dog. J. Philippe Rushton is a professor of psychology at the University of Western Ontario, London, Ontario, Canada. Rushton holds two doctorates from the University of London (Ph.D.
and initiativeblog.com) and is a Fellow of the John Simon Guggenheim Foundation, the American Association for the Advancement of Science, and the American, British, and Canadian Psychological Associations.
The co-evolution of scientific knowledge, images of science, and strategies for knowledge acquisition is a complex process that has hardly been understood, also because the history of scientific knowledge and the sociology of scientific institutions have been traditionally studied separate from each other.
Consequently, the spread of. acquired trait: A phenotypic characteristic, acquired during growth and development, that is not genetically based and therefore cannot be passed on to the next generation (for example, the large.
Nature of scientific knowledge. Origin and evolution of the earth system. Natural resources. Historical perspectives. Origin and evolution of the universe. Environmental quality. Natural and human-induced hazards.
Science and technology in local, national, and global challenges.