top of page
Search

Subspecies

  • Writer: Lafyva
    Lafyva
  • May 24, 2020
  • 7 min read

Updated: Aug 24


In biological terms, rather than in relation to nomenclature, a polytypic species has two or more genetically and phenotypically divergent subspecies, races, or more generally speaking, populations that differ from each other so that a separate description is warranted.[16] These distinct groups do not interbreed as they are isolated from another, but they can interbreed and have fertile offspring, e.g. in captivity. These subspecies, races, or populations, are usually described and named by zoologists, botanists and microbiologists.
In the wild, subspecies do not interbreed due to geographic isolation or sexual selection. The differences between subspecies are usually less distinct than the differences between species.


The Subspecies Designation
Most modern concepts (Haig et al., 2006), including one suggested by Darwin, rely on the notion of a partial restriction of gene flow. Virtually all modern definitions of subspecies follow the spirit of these original definitions, with the general view being that subspecies are groups of actually or potentially interbreeding populations that are phylogenetically distinguishable from, but reproductively compatible with, other such groups (Mayr, 1953, 1963; Mayr and Ashlock, 1991).


AI Overview

The phrase "phylogenetically distinguishable from, but reproductively compatible with, other such groups" describes a subspecies. Subspecies are populations within a species that exhibit distinct characteristics due to differences in their evolutionary history, yet can still interbreed and produce fertile offspring with other subspecies. This concept highlights the interplay between evolutionary divergence and gene flow within a species.

Here's a more detailed explanation:

  • Phylogenetically Distinguishable: This means that the group has a unique evolutionary history, often reflected in genetic differences and sometimes in observable morphological traits.

  • Reproductively Compatible: Despite the evolutionary differences, individuals from different subspecies can still interbreed and produce viable, fertile offspring.

  • Other Such Groups: This refers to other subspecies within the same species.

In essence, a subspecies represents a stage in the process of speciation where populations are diverging but haven't yet reached the point of complete reproductive isolation that would define them as separate species. The concept of subspecies is particularly relevant in understanding patterns of geographic variation and the early stages of evolutionary divergence.



{[{ Disassortative mating (sometimes called negative assortative mating) occurs when mates are chosen to be more phenotypically dissimilar  than would arise by chance alone. Disassortative mating is not only the opposite of assortative mating in terms of the phenotypes displayed by mating pairs but also in its evolutionary and genetic consequences.


 A potential example of disassortative mating in humans is

 the major histocompatibility complex (MHC)


 Assortative mating by “ethnicity” has been historically quite strong and reduces genetic admixture among the descendants of these historic populations


 When “ethnicity” and other sociocultural biases that influence mate choice are not controlled, it appears as if there is assortative mating for MHC, but when these factors are eliminated or controlled, it appears as if there is disassortative mating for MHC








Hardy–Weinberg Equilibrium

The Hardy–Weinberg equilibrium provides the cornerstone for our understanding of population genetics. The concept was established in 1908 independently by the English mathematician G.H. Hardy and the German physician W. Weinberg. Their formulation states a simple relationship between the frequency of alleles at a genetic locus and the genotypes resulting from those alleles. Consider a gene locus with alleles A and a. Let the frequency of A be designated by the variable p and the frequency of a by the variable q. If all alleles at this locus are either A or a, then p + q = 1. The frequency of sperm or egg cells in the population carrying A or a will thus be p or q, respectively (Figure 7.1). If we assume that the union of germ cells carrying either A or a is entirely random, we can easily calculate the frequency of zygotes having the genotype AA, Aa, or aa. The frequency of AA will be p2 and of aa will be q2. The frequency of heterozygotes will be 2pq, reflecting that Aa individuals can arise in two ways: fusion of A-bearing sperm with a-bearing eggs, or vice versa (Methods 7.1).

















An international consortium today published a third-generation map of human genetic variation, called the HapMap, which includes data from an additional seven global populations, increasing the total number to 11 populations.

Any two humans are more than 99 percent the same at the genetic level.


Figure 11.4 Jefferson’s Family Many people have become accustomed to viewing racial groups as natural and separate divisions within our species based on visible physical differences. However, these groups differ from one another in only 7 percent of their genes. For many thousands of years, individuals belonging to different human social groups have been in sexual contact. Exchanging their genes, they maintained the human species in all its colorful variety and prevented the development of distinctive subspecies (biologically defined races). This continued genetic mixing is effectively illustrated by the above photo of distant relatives, all of whom are descendants of Sally Hemings, an African American slave, and Thomas Jefferson, the Anglo-American gentleman-farmer who had 150 slaves working for him at his Virginia plantation and served as third U.S. president (1801–1809).


Human Population Genetic Structure and Inference of Group Membership

Eighty-five to ninety percent of neutral genetic variation

in the human species is due to differences between individuals

within populations (Lewontin 1972; Barbujani

et al. 1997; Jorde et al. 2000). The remaining 10%–15%

is distributed between groups, and, though modest,


Microsatellite Markers (simple sequence repeats, SSRs)
Genetic Linkage





Genomic evidence for MHC disassortative mating in humans


Linkage Disequilibrium







It is widely accepted that race differences in intelligence exist, but no consensus has emerged on whether these have any genetic basis. The present book is the first fully comprehensive review that has ever been made of the evidence on race differences in intelligence worldwide. It reviews these for ten races rather than the three major races (Africans, Caucasians, and East Asians) analyzed by Rushton (2000). The races analyzed here are the Europeans, sub-Saharan Africans, Bushmen, South Asians and North Africans, Southeast Asians, Australian Aborigines, Pacific Islanders, East Asians, Arctic Peoples, and Native American Indians. Studies of these are presented in Chapters 3 through 12; Chapter 13 summarizes these studies and gives evidence on the reliability and validity of the IQs of the races. Chapter 14 discusses the extent to which race differences in intelligence are determined by environmental and genetic factors. Chapters 15, 16, and 17 discuss how race differences in intelligence have evolved over the course of approximately the last 100,000 years. These discussions are preceded by accounts of the nature of intelligence and the measurement of race differences given in the first chapter, and of the concept of race in Chapter 2. (PsycINFO Database Record (c) 2016 APA, all rights reserved)








Neuroanatomy

Prefrontal cortex interactions with the amygdala in primates

The PFC plays a role in creative ideation and problem solving by providing a control mechanism (Cassotti et al., 2016; Diamond, 2013; Khalil et al., 2018b, 2019, 2020;

Kriete et al., 2013).

A neurocomputational model of creative processes

The Chinese population showed greater structural features in the

temporal lobe and cingulate gyrus, and smaller features in the frontal

lobe and parietal lobe, compared with the Caucasian cohort. https://pubmed.ncbi.nlm.nih.gov/29400417/

The Caucasian group showed greater density and

volume in the medial prefrontal lobes, the superior and middle frontal

gyri, the motor speech area (Broca’s area), the precentral and postcentral

gyri, the angular gyri and the orbitofrontal gyri bilaterally, the left

inferior occipital gyrus, and the left paracentral lobule (Figure 4).


ree

ree

Overall, the PFC enables the formation and control of mental representations according to an internal goal by selecting information from the environment or from memory, by forming or selecting rules, and by resisting spontaneous prepotent responses (Levy and Volle, 2009). These prefrontal properties are assumed to support creativity as well as complex human abilities such as planning, reasoning, problem solving, abstract thinking (Carlsson et al., 2000; Godefroy, 2003; Dietrich, 2004; Bogousslavsky, 2005; Changeux, 2005; Burgess et al., 2009; Levy and Volle, 2009). In other words, our knowledge of PFC structure and functions supports the assumption that the PFC is essential for cognitive processes that underlie creative thinking. Experimental studies using creativity tasks in healthy participants and in patients confirm this hypothesis.


Functional neuroimaging and experimental patient studies also suggest that the PFC, in particular the anterior PFC, may also play a critical role in originality aspects of creativity.



ree



AI Overview

Learn more

The "medial prefrontal lobes, superior and middle frontal gyri, orbitofrontal gyri bilaterally" refers to a group of brain regions located within the prefrontal cortex, specifically encompassing the medial section of the frontal lobes including the superior and middle frontal gyri, as well as the orbitofrontal gyri on both sides of the brain; essentially describing a large network of brain areas involved in complex cognitive functions like decision making, social behavior, and emotional regulation.


AI Overview

Learn more

According to research, studies generally indicate that Caucasians tend to have a larger prefrontal cortex compared to East Asians, showing greater gray matter volume in the medial prefrontal cortex and orbitofrontal cortex in Caucasian populations compared to East Asians; however, it's important to note that these findings can vary based on specific studies and individual differences within each population.










AI Overview


The "K-factor" in the context of life history theory refers to a single, underlying factor that influences various life history traits within a population. It represents an individual's position on a continuum of "fast" to "slow" life history strategies. While the K-factor is often discussed in the context of racial and ethnic differences, it's important to understand that it also operates within ethnic groups.











Tracing the origin and spread of agriculture in Europe
Scholars have considered that the typical plants and animals exploited by modern North African farmers (e.g., wheat, barley, sheep, goats, and cattle) were introduced in their domesticated form from outside the continent, most likely from southwestern Asia. Evidence from Egypt and the Sahara, however, suggests that a degree of indigenous African domestication may have preceded the introduction of Eurasian domesticates. In particular, the evidence from Nabta Playa in the western desert of Egypt indicates that semisedentary populations were living there before 8 Ka and that they were collecting and storing wild sorghum with a possible selective effect in the direction of domestication. Furthermore, the predominance of cattle bones among the bones of gazelles and other animals adapted to semiarid savannah suggests that cattle were probably being kept or watered by humans, and thus the initial conditions of domestication were satisfied. Mitochondrial DNA studies confirm that African and Eurasian domestic cattle belong to separate races whose split predates the earliest possible dates for domestication in either region.
Eric Delson, Ian Tattersall, John A. Van Couvering and Alison S. Brooks. Encyclopedia of Human Evolution and Prehistory (Garland Reference Library of the Humanities) (Kindle Locations 2363-2371). Taylor and Francis. Kindle Edition.


Human Population Genomics

 
 
bottom of page