Duration (million Eons Eras Periods Epochs years ago)
Hadean 4500–3800 Archaean 3800–2500 Proterozoic 2500–540 Ediacaran 600–540 Phanerozoic 540– Paleozoic 540–250 Cambrian 540–510 Ordovician 510–440 Silurian 440–410 Devonian 410–360 Carboniferous 360–290 Permian 290–250 Mesozoic 250–65 Triassic 250–210 Jurassic 210–140 Cretaceous 140–65 Cenozoic 65– Tertiary 65–2 Paleocene 65–55 Eocene 55–35 Oligocene 35–25 Miocene 25–5 Pliocene 5–2 Quaternary 2– Pleistocene 2–0.01 Holocene 0.01– Note: The complete list of periods is presented only for the Phanerozoic Eon. Note: The complete list of epochs is presented only for the Cenozoic era. Note: The Holocene epoch is also called the Recent epoch.
Note: The Cenozoic era is now frequently divided into the Paleogene period (Paleocene, Eocene, Oligocene epochs) and the Neogene period (Miocene, Pliocene, Pleistocene, and Holocene epochs).
animals, and the changes that occurred during the course of human evolution, it is necessary to thoroughly study the behavior of other animals, especially chimpanzees, under natu- ral conditions. This required many years of close observation and the ability to recognize individual chimpanzees. Goodall’s close and prolonged observation yielded surprises that other researchers of animal behavior had not seen.
Goodall was born April 3, 1934. In 1960 Goodall began observations in the Gombe Preserve in Tanzania. One persistent problem in the study of animal behavior (see behavior, evolution of) is that the behavior of the animals, particularly intelligent ones like chimpanzees, is altered by the presence of human observers. Months passed before the chimpanzees allowed Goodall to approach them closely enough for observation. Once they had accepted her, she was able to observe their normal lives. In her first year of observation Goodall made two discoveries. First, she found that chimpanzees hunt and eat meat. Second, she found that chimpanzees use tools. She observed chimps stripping leaves from twigs and using the twigs to fish ter- mites out of a nest. This observation proved that humans were not the only animals that made and used tools (see technology). Goodall earned her Ph.D. in ethology from Cambridge University in 1965.
Soon thereafter Goodall returned to Tanzania and established the Gombe Stream Research Center. She con- tinued to make observations that showed chimpanzees to be capable of behavior previously associated only with humans. Particularly striking is the complexity of chim- panzee social organization and the advance planning that allows it. She observed a female chimpanzee adopt an unre- lated baby chimpanzee. Chimpanzees were also capable of actions that remind observers of the bad side of human behavior. In 1974 a four-year war began between two bands of chimpanzees, resulting in the annihilation of one. Goodall also observed one chimpanzee that cannibalized several infants. Perhaps the most striking observation was in 1970 when Goodall observed chimpanzees apparently dancing for joy in front of a waterfall. All of these obser- vations call into question the vast gulf that most people, including many scientists, assume to exist between humans and other animal species, and demonstrate that individual chimpanzees can differ as much from one another as indi- vidual humans.
Goodall is interested in far more than just understand- ing animal behavior. She began and continues efforts to rescue orphaned chimpanzees and to improve the condi- tions of chimpanzees that are used in medical research. The president of a medical research company who at first despised Goodall’s interference ended up thanking her for her work. In 1977 Goodall founded the Jane Goodall Institute for Wildlife Research, Education, and Conserva- tion, which encourages local people in Africa and all over the world to undertake conservation efforts in their own region. Her work both in the scientific study of behavior and in conservation have earned her many awards and worldwide recognition.
Further Reading
Goodall, Jane, and Phillip Berman. Reason for Hope: A Spiritual Journey. New York: Warner Books, 1999.
Jane Goodall Institute. “The Jane Goodall Institute.” Available online. URL: http://www.janegoodall.org. Accessed March 28, 2005. Miller, Peter. “Jane Goodall.” National Geographic, December 1995,
102–129.
Peterson, Dale. Jane Goodall: The Woman Who Redefined Man. New York: Houghton Mifflin, 2006.
Gould, Stephen Jay
(1941–2002) American Evolutionary biologist Stephen Jay Gould was one of the most creative thinkers in the study of evolution and one of the most famous and effective popularizers of evolution to the general public. His first scientific book, Ontogeny and Phylogeny, and his first pop- ular book, Ever Since Darwin, were both published in 1977.Born September 10, 1941, Gould became interested in evolution when he was five years old and saw the Tyranno- saurus skeleton at the American Museum of Natural History in New York. He stayed with his youthful decision to become an evolutionary scientist. After graduating from Antioch Col- lege, Gould earned his Ph.D. from Columbia University. Until his death he was a professor at Harvard University and a curator at Harvard’s Museum of Comparative Zoology.
One of Gould’s insights into evolution was that evolu- tion was not entirely a gradual process. Instead, periods of rapid change, associated with the appearance of a new spe- cies (see speciation), were followed by long periods of sta- sis. Together with a colleague at the American Museum of Natural History (see Eldredge, Niles), Gould presented the theory of punctuated equilibria in 1972. Gould, Eldredge, and Yale paleontologist Elisabeth Vrba maintained that evolu- tion occurs not just on the level of populations (see natural selection) but on the species level as well. While defending the proof of evolution and the mechanism of natural selec- tion that Darwin had presented (see Darwin, Charles; origin of species [book]), Gould maintained that Darwin had unnecessarily constrained the operation of evolution by claiming that it always occurred gradually. Gould summa- rized a lifetime of insights into the processes of evolution in The Structure of Evolutionary Theory. Another major insight was that many features of organisms were not adaptations but were side effects of adaptations, resulting from structural constraints. Gould and paleontologist Elisabeth Vrba called these features exaptations (see adaptation).
A related insight was that chance events have played a major role in the histories of individual humans, of societies, of species, and of the entire Earth. Gould’s doctoral research focused on land snails (genus Cerion) in Bermuda. He closely studied the individual variations among these snails, the same way that Darwin focused upon barnacles. Gould found that many of the variations could be better explained as the prod- ucts of chance, or of structural constraint, than of adaptation. Gould also survived cancer for more than two decades. This experience contributed to his thinking about the importance of chance events. Gould’s 1989 book Wonderful Life made the fossils of the Burgess shale, from a 510-million-year-old Gould, Stephen Jay
marine environment of the Cambrian period, well known to the general public. He claimed that these fossils demonstrated an early diversification of life, followed by the extinction of many lineages. Had the lineage that led to vertebrates become extinct, something that could have happened by chance, humans might not exist at all. Gould’s 1996 book Full House explained what appeared to be progress, whether in evolu- tion or in baseball, to results from chance events followed by unequal success, rather than an inherent upward progression (see progress, concept of).
For several decades, Gould contributed columns enti- tled “This View of Life” to Natural History magazine and collected them into popular books. These essays also reveal Gould’s great breadth of knowledge into almost every sub- ject, and his ability to connect them. He also made many readers aware (in his book The Mismeasure of Man) of how science can be used by some humans to oppress others, as in the pseudoscience of eugenics. Gould was also a major con- tributor to the educational campaign against creationism, which, as he explained in Rocks of Ages, he considered an unnecessary pitting of religion against science. As a result of his popular writings, Gould made almost every aspect of evo- lution, from the history of the development of the theory, to the evidence that supports it, to the way it works, accessible and interesting to the general public. He died May 20, 2002. Further Reading Eldredge, Niles, and Stephen Jay Gould. “Punctuated equilibria: An alternative to phyletic gradualism.” In Models in Paleobiology, edited by T. J. M Schopf, 82–115. San Francisco, Calif.: Freeman, Cooper and Co., 1972.
Gould, Stephen Jay. Bully for Brontosaurus. New York: Norton, 1991.
———. Crossing Over: Where Art and Science Meet. New York: Three Rivers Press, 2000.
———. Dinosaur in a Haystack. New York: Harmony Books, 1995. ———. Eight Little Piggies. New York: Norton, 1993.
———. The Flamingo’s Smile. New York: Norton, 1985.
———. Full House: The Spread of Excellence from Plato to Darwin. New York: Harmony Books, 1996.
———. Leonardo’s Mountain of Clams and the Diet of Worms. New York: Harmony Books, 1998.
———. The Lying Stones of Marrakech. New York: Harmony Books, 2000.
———. The Hedgehog, the Fox, and the Magister’s Pox. New York: Harmony Books, 2003.
———. Hen’s Teeth and Horse’s Toes. New York: Norton, 1983. ———. I Have Landed: The End of a Beginning in Natural History.
New York: Harmony Books, 2002.
———. The Mismeasure of Man. New York: Norton, 1981. ———. Ontogeny and Phylogeny. Cambridge, Mass.: Harvard Uni-
versity Press, 1977.
———. The Panda’s Thumb. New York: Norton, 1980.
———. Questioning the Millennium: A Rationalist’s Guide to a Pre- cisely Arbitrary Countdown. New York: Harmony Books, 1997. ———. Rocks of Ages: Science and Religion in the Fullness of Life.
New York: Ballantine Publications, 1999.
———. The Structure of Evolutionary Theory. Cambridge, Mass.: Harvard University Press, 2002.
———. Time’s Arrow, Time’s Cycle. Cambridge, Mass.: Harvard University Press, 1987.
———. An Urchin in the Storm: Essays about Books and Ideas. New York: Norton, 1987.
———. Wonderful Life: The Burgess Shale and the Nature of His- tory. New York: Norton, 1989.
———, and Richard Lewontin. “The spandrels of San Marco and the Panglossian paradigm: A critique of the adaptationist pro- gramme.” Proceedings of the Royal Society of London B 205 (1979): 581–598.
Grant, Peter
See Darwin’s finches.Grant, Rosemary
See Darwin’s finches.Gray, Asa
(1810–1888) American Botanist, Evolutionary Scientist Asa Gray was an early defender of Darwinian evo- lution in the United States. He was representative of a large number of English and American scientists and theologians who accepted evolutionary science while maintaining their traditional Christian beliefs. Antievolutionists, also called cre- ationists (see creationism), were much more common in the 20th century than in the half century following the publication of Darwin’s Origin of Species (see Darwin, Charles; origin of species [book]). Gray is representative of the Christian scholars who embraced Darwinian science, not only because of Gray’s prominence but also because he was a personal cor- respondent of Charles Darwin even before the publication of the Origin of Species. Born November 18, 1810, Gray was trained as a medical doctor. Even while practicing medicine, his main interest was the study of plants. He learned much from America’s leading botanist, John Torrey, and by 1831 Gray was ready to aban- don medical practice and pursue botany full-time. For the next five years, he conducted botanical investigations with Torrey, which culminated in their coauthorship of the Flora of North America. Gray spent a year as a member of the sci- entific corps of the American Exploring Expedition in Europe and also studied what was just becoming known about Jap- anese botany. In 1842 he received a faculty appointment in natural history at Harvard University.It was not only botany that Gray learned from Torrey. Torrey’s firm Presbyterian faith led Gray to consider his own, and in 1835 Gray underwent a Christian conversion experi- ence. Gray found that Christianity led him to investigate sci- ence ever more enthusiastically. Gray put his faith into action by church work that included teaching a black Sunday school class at a time when prejudice against African Americans was still standard, even in the North. At this time, as a devotee of William Paley (see natural theology) and opponent of Chambers’s Vestiges of Cre- ation (see Chambers, Robert), Gray resisted the idea of the transmutation of species (today called evolution). In this, he was consistent with most scientists of his time. He did not use the Bible as a source of information about Earth history;
he had long accepted Lyell’s geology (see Lyell, Charles; uniformitarianism) and accommodated his interpretation of the biblical book of Genesis accordingly. He was experi- encing difficulty in explaining many facts of botany, in par- ticular the similarity of plant genera in North America and eastern Asia. It looked to him as though these plants had not been separately created but were the descendants of a com- mon flora that had been pushed southward by glaciation (see ice ages).
Gray’s scientific reputation grew from his insistence upon facts over speculation, and this is what brought him to the attention of Charles Darwin. When Darwin wanted a botanist in whom to confide about his slowly developing evolutionary theory, he turned to Gray, even though on the other side of the Atlantic, as well as to botanist Sir Joseph Hooker (see Hooker, Joseph Dalton). Reading Darwin’s manuscript of the Origin of Species convinced Gray that transmutation of species had occurred and would solve the botanical mysteries he had been studying. Gray announced this conclusion at a scientific meeting in January 1859, before the appearance of Darwin’s book. Once the Origin of Species had appeared later that year, Gray was in the perfect position to defend it. In defending Darwinian evolution, Gray came in public conflict with his Harvard colleague, Louis Agassiz (see Agas- siz, Louis), particularly during a public debate in 1859. This debate was very different from what one might expect to see today: Agassiz, the Unitarian who rejected biblical reliabil- ity, attacked Darwinian evolutionary science, while Gray, the Christian who believed in the inspiration of the Bible, defended it. They had many points of conflict, not the least of which was one of the major issues on the minds of peo- ple that year: the impending possibility of War Between the States. Agassiz believed that different races were separately created by God, and that God intended some of them (whom he considered inferior) to be dominated by others. Gray believed that all races of humankind had a common origin, and that each individual had equal worth.
Darwin appreciated Gray’s support, even though Dar- win’s agnosticism differed profoundly from Gray’s Christi- anity. Darwin told Gray that he had never intended to write atheistically; but he could not see the world, as Gray did, to be the creation of a beneficent God. There was, Darwin said, too much misery in the world. Darwin was willing to admit that the general laws of nature may have a divine origin, but he could not see evidence of design in the particulars. These admissions on Darwin’s part are nearly all that historians have of his religious doubts, as Darwin resisted public debate even about evolutionary science, not to mention religion.
Gray accepted evolutionary science, albeit in a form dif- ferent from what scientists understand today, but resisted what he considered a fanciful extension of evolutionary sci- ence into the kind of social Darwinism that was being pro- moted by writers such as Spencer (see Spencer, Herbert).
Even while accepting Darwinian evolution, however, Gray still admired Paley’s natural theology. This was the one point at which Gray differed from Darwin: Gray believed
that the evolutionary process has a purpose or direction, a concept subsequently called teleology. Gray believed that God guided the evolutionary process in directions that would suit God’s ultimate purposes. This occurred, he believed, because God created the heritable variation within populations upon which natural selection depended. Since the science of genet- ics was unknown prior to Mendel (see Mendel, Gregor; Mendelian genetics), there was no proof against this con- cept. By adding teleology to evolution, Gray thought that he had reconciled Paley’s Natural Theology with Darwin’s evo- lution. Even though Darwin knew that this reconciliation was unlikely, he was pleased at the attempt; he reprinted three of Gray’s essays at his (Darwin’s) own expense, with “Natural Selection Not Inconsistent With Natural Theology” printed at the top. The concept of teleology is rejected by scientists today, as there is no known physical or chemical mechanism for it; it is a religious concept.
Adding teleology to Darwinian evolution was the same accommodation that the other Christian evolutionists of the late 19th century made, and which allowed them to accept a form of evolutionary science. These included geologists George Frederick Wright and James Dwight Dana. Wright, a minister and geologist, later on the faculty of Oberlin Col- lege, worked with Gray on some of Gray’s last publications about science and religion. Wright insisted that while God was the primary cause of the existence of everything, Dar- winian science adequately explained the secondary causes. Wright even saw parallels between evolutionary science and some traditional Calvinist doctrines such as original sin. Dana was a geologist, later at Yale, whose around-the-world journey while he was young transformed his outlook as much as the Beagle voyage had influenced Darwin. This was almost the same time that Dana had a religious conversion experi- ence. He, like Gray, had his view of an orderly, created world shaken by reading Darwin’s Origin of Species. He resisted it at first, but in later works admitted that the history of the Earth had occurred by means of evolution. He pointed out, as do many Christian writers today, that Genesis 1 phrases such as “let the Earth bring forth” allowed, even encour- aged, a belief in secondary causes such as evolution. Gray and others believed that God’s world was designed to make itself, design was seen not in the organisms themselves but in the overall system of natural laws that had produced them. They believed that the “image of God” referred to in Genesis 1 was not the physical body of humans but the spirit; and that an animal origin of humankind was no more demean- ing than what Genesis 1 said: that humans were made of dirt. A number of famous late-19th-century preachers, such as A. H. Strong and Henry Ward Beecher, actually praised Darwin- ian evolution in part because it removed some of the difficul- ties that had been faced by the old style Natural Theology. It had previously been difficult to explain why a world created by a good God would contain so much apparent evil; now these ministers, and religious scientists, could claim that these evils such as the death of the less fit were a necessary part of God’s evolutionary system of creation. In this, they followed the lead of Asa Gray.
In the 20th century, many creationists proclaimed that evolutionary science is incompatible with belief in God. Asa Gray, and many other scientists and theologians of the 19th century, show that this is not true. Gray died January 30, 1888.
Further Reading
Livingstone, David N. Darwin’s Forgotten Defenders. Grand Rap- ids, Mich.: Eerdmans; Edinburgh, U.K.: Scottish Academic Press, 1987.