V. The Origins of Humanity and the Mechanisms of Inheritance
Since the beginning of time, humans have questioned their origins. Earliest explanations focused on mystical/magical and spiritual forces, often centered on creationism, the theory that life originated from a divine source. The power of the organized religions in shaping man’s social, political, economic, and legal systems is testament to their immense influence. For example, religious perspectives dominated philosophical thought until the Scientific Revolution began in the mid-16th century, when advances in theory and practice provided explanations alternative to those promulgated by the church. Galileo Galilei (1564–1642), Johannes Kepler (1571–1630), Rene Descartes (1596–1650), and Isaac Newton (1643–1727) all made significant contributions that brought scientific reasoning to the forefront of thought as a competitor to spiritual explanations. Although usurping the philosophies of the church were not their main goals, their revolutionary ideas (that natural events and human behaviors may be explained by the development and application of certain scientific principles) had just that effect. Needless to say, secular science was not very popular with the church and organized religion. However, these changes were vital in advancing understanding of human and societal behavior.
A. Persistence of Human Traits and Characteristics
In addition to having been the potential source of physiognomy, ancient Greek philosophers also were among the first to recognize and attempt to explain the persistence of traits and characteristics from one generation to the next. Plato and Aristotle used the concept of association to explain how current mental processes (especially memories) generate from prior mental processes. These beliefs broadened to include all mental processes in the hands of philosophers such as Hume, Mill, and Locke.
Given that memories and other, possibly undesirable, characteristics and traits could potentially persist through generations, Plato advocated the control of reproduction by the state (government). Infanticide was practiced as a form of population control in ancient Rome, Athens, and Sparta. Many of the ancient societies also engaged in practices to weed out weak, diseased, malformed, or otherwise unfit members, such as exposing young children to the elements to see which ones had the strength, intelligence, and wit to survive.
Scientists began studying the nature of persistent traits in plants and animals prior to the application of these ideals to humans. Once established, however, it took relatively little time and relatively little effort to explain human patterns with these principles. As readers will note, the mid- to late 18th century was characterized by rapid progress in the natural sciences, which positively impacted biologically oriented research in the social sciences.
1. Carolus (Carl) Linnaeus (1707–1778)
Linnaeus, a Swedish botanist, zoologist, and physician, was among the first to document traits, patterns, and characteristics among plants and animals, creating hierarchical taxonomies (systems of classification). In Systema Naturae (System of Nature), published in 1735, Linnaeus grouped humans with other primates, becoming one of the first to recognize similar characteristics across species, hinting at an evolutionary progression.
2. Pierre-Louis Moreau de Maupertuis (1698–1759)
In 1745, French philosopher and mathematician Maupertuis published Venus Physique (Physical Venus), in which he proposed a theory of reproduction in which organic materials contained mechanisms to naturally organize. He subsequently discussed his views on heredity and examined the contributions of both sexes to reproduction, examining variations through statistics. Whether Maupertuis can be credited with being among the first to attempt to elucidate a theory of evolution is actively debated. He is generally credited with outlining the basic principles of evolutionary thought, along with his contemporary, James Burnett (see James Burnett, Lord Monboddo [1714–1799] section).
3. David Hartley (1705–1757) and the Associationist School
Hartley (borrowing somewhat from philosopher John Locke) published his most influential work—Observations on Man, His Frame, His Duty, and His Expectations—in 1749. In it, he attempted to explain memory and thought, in general, through the doctrine of association. This was significant, because he attempted to link the processes of the body to the processes of the brain. He explained that actions and thoughts that do not result immediately from an external stimulus are influenced by the constant activity of the brain because of man’s past experiences, mediated by the current circumstances, causing man to act in one way or another. This brain activities that Hartley called sensations are often associated together and become associated with other ideas and sensations, forming new ideas. Hartley’s work was important in that it brought scientific focus to the process of thought, the origin of emotions, and the impact of feelings on the creation of voluntary action. This is a positivist philosophy in that action is not viewed as being the direct result of strict free will.
4. George-Louis Leclerc, Comte de Buffon (1707–1788)
From 1749 to 1778, Leclerc published his most famous and influential work in 36 volumes, with an additional 8 volumes published postmortem. It was a study of natural history, from the general to the specific. In this work, he proposed the idea that species, including humans, change (i.e., evolve) throughout generations. Following in the footsteps of Linnaeus, he also proposed the radical idea of a relationship between humans and apes.
In another controversial publication, The Eras of Nature (1778), Leclerc questioned the long-standing and sacred belief that the universe was created by a divine power, instead suggesting that our solar system was created by celestial collisions. Finally, he contradicted the notion that seemingly useless body parts on animals were spontaneously generated but instead were vestigial, remnants of evolutionary progress.
Leclerc’s influence was widespread and impacted subsequent beliefs about the transmission of traits from one generation to the next (inheritance, heredity) as well as about changes that occur over time with each passing generation (evolution). These ideas significantly impacted biological theories of behavior. Charles Darwin, in fact, credited Leclerc with being the first modern author of the time to treat evolution as a scientific principle.
5. James Burnett, Lord Monboddo (1714–1799)
Burnett, a Scottish judge, is credited with being another of the first to promote evolutionary ideas, in particular, the idea of natural selection. In The Origin and Progress of Language (1773), Burnett analyzed the development of language as an evolutionary process; he clearly was familiar with the ideas of natural selection, although he differed with Leclerc in his support of the notion that humans were related to apes.
6. Erasmus Darwin (1731–1802)
One individual who took Leclerc’s ideas to heart was Erasmus Darwin, grandfather of Charles Darwin and Francis Galton (see subsequent sections on Charles Darwin and Galton). Darwin also integrated ideas from Linnaeus, translating Linnaeus’s works from Latin to English and publishing his own book of poetry about plants, The Botanic Garden (1791). Between 1794 and 1796, Darwin published Zoonomia, which discussed the concept of generation (reproduction) and used Hartley’s theory of association (and possibly Linneaus’s taxonomies). Many scholars believe Darwin’s propositions were the forerunners of amore well-defined theory of inheritance later argued by Jean- Baptiste Lamarck (see Jean-Baptiste Lamarck [1744–1829] section).
7. Thomas Robert Malthus (1766–1834)
In 1798, Malthus, an English demographer and political economist, published An Essay on the Principle of Population, in which he proposed that populations struggle for existence in competition over resources. His main premise was that increases in population result in increased competition for scarce resources, primarily food. As a society becomes overpopulated, those at the bottom of the socioeconomic strata suffer the most (and often die). He explained that some natural events and conditions serve to control population growth (e.g., war, disease, famine) and that moral restraint (e.g., abstinence, late marriage) could serve the same function.
Contrary to many economists of the time who believed that increasing fertility rates and populations would provide more workers and would increase the productivity of a society, Malthus argued that the provision of resources could often not keep pace with population growth and would result in more poverty among the lower classes. This depiction of a struggle for existence was applied by subsequent scientists to plants and animals and was instrumental to Charles Darwin (and others) in arguments about “natural selection” and “survival of the fittest” (a phrase coined by Herbert Spencer; see Herbert Spencer [1820–1903] section).
8. Jean-Baptiste Lamarck (1744–1829)
Lamarck was a French naturalist, mentored by Leclerc (see preceding section on Leclerc), who published Recherches sur l’Organisation des Corps Vivans (Research on the Organization of Living Things) in 1802. Lemarck was among the first to attempt to classify invertebrates and was among the first to use the term biology. He primarily is known for promoting and advocating a theory of soft inheritance, or inheritance of acquired characters, in which characteristics developed during the lifetime of an organism (e.g., larger or stronger muscles) are passed along to subsequent generations, making them better suited for survival (or better adapted).
Lemarck is considered the first to articulate a coherent theory of evolution, although he believed that organisms came into being through spontaneous generation instead of sharing a common source. His theory was characterized by two main arguments: (1) that organisms progress from simpler to more complex through generations and (2) that organisms develop adaptations because of their environments or because of the necessity (or lack thereof) of particular characteristics (the use-it-or-lose-it aspect).