''River Out of Eden: A Darwinian View of Life'' is a 1995
popular science
''Popular Science'' (also known as ''PopSci'') is an American digital magazine carrying popular science content, which refers to articles for the general reader on science and technology subjects. ''Popular Science'' has won over 58 awards, incl ...
book by
Richard Dawkins
Richard Dawkins (born 26 March 1941) is a British evolutionary biologist and author. He is an emeritus fellow of New College, Oxford and was Professor for Public Understanding of Science in the University of Oxford from 1995 to 2008. An ath ...
. The book is about
Darwinian
Darwinism is a theory of biological evolution developed by the English naturalist Charles Darwin (1809–1882) and others, stating that all species of organisms arise and develop through the natural selection of small, inherited variations that ...
evolution
Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes, which are passed on from parent to offspring during reproduction. Variation ...
and summarizes the topics covered in his earlier books, ''
The Selfish Gene
''The Selfish Gene'' is a 1976 book on evolution by the ethologist Richard Dawkins, in which the author builds upon the principal theory of George C. Williams's ''Adaptation and Natural Selection'' (1966). Dawkins uses the term "selfish gene ...
'', ''
The Extended Phenotype
''The Extended Phenotype'' is a 1982 book by the evolutionary biologist Richard Dawkins, in which the author introduced a biological concept of the same name. The main idea is that phenotype should not be ''limited'' to biological processes such ...
'' and ''
The Blind Watchmaker
''The Blind Watchmaker: Why the Evidence of Evolution Reveals a Universe without Design'' is a 1986 book by Richard Dawkins, in which the author presents an explanation of, and argument for, the theory of evolution by means of natural selecti ...
''. It is part of the
''Science Masters'' series and is Dawkins's shortest book. It is illustrated by
Lalla Ward
Sarah Jill "Lalla" Ward (born 28 June 1951) is an English actress, voice artist and author. She is best known for playing the role of Romana II in the BBC television series ''Doctor Who'' from 1979 to 1981.
Career
Early career
Ward's stage na ...
, Dawkins's wife. The book's name is derived from Genesis 2:10 relating to the
Garden of Eden
In Abrahamic religions, the Garden of Eden ( he, גַּן־עֵדֶן, ) or Garden of God (, and גַן־אֱלֹהִים ''gan-Elohim''), also called the Terrestrial Paradise, is the Bible, biblical paradise described in Book of Genesis, Genes ...
. The
King James Version
The King James Version (KJV), also the King James Bible (KJB) and the Authorized Version, is an Bible translations into English, English translation of the Christian Bible for the Church of England, which was commissioned in 1604 and publis ...
reads "And a river went out of Eden to water the garden; and from thence it was parted, and became into four heads."
''River Out of Eden'' has five chapters. The first chapter lays down the framework on which the rest of the book is built, that life is like a river of
gene
In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a ba ...
s flowing through
geological time
The geologic time scale, or geological time scale, (GTS) is a representation of time based on the rock record of Earth. It is a system of chronological dating that uses chronostratigraphy (the process of relating strata to time) and geochron ...
where
organism
In biology, an organism () is any living system that functions as an individual entity. All organisms are composed of cells (cell theory). Organisms are classified by taxonomy into groups such as multicellular animals, plants, and ...
s are mere temporary bodies. The second chapter shows how human ancestry can be traced via many gene pathways to different ''
most recent common ancestor
In biology and genetic genealogy, the most recent common ancestor (MRCA), also known as the last common ancestor (LCA) or concestor, of a set of organisms is the most recent individual from which all the organisms of the set are descended. The ...
s'', with special emphasis on the ''
African Eve
In human genetics, the Mitochondrial Eve (also ''mt-Eve, mt-MRCA'') is the matrilineal most recent common ancestor (MRCA) of all living humans. In other words, she is defined as the most recent woman from whom all living humans descend in an un ...
''. The third chapter describes how gradual enhancement via natural selection is the only mechanism which can create the observed complexity of nature. The fourth chapter describes the indifference of genes towards organisms they build and discard, as they maximise their own
utility function
As a topic of economics, utility is used to model worth or value. Its usage has evolved significantly over time. The term was introduced initially as a measure of pleasure or happiness as part of the theory of utilitarianism by moral philosopher ...
s. The last chapter summarises milestones during the evolution of life on
Earth
Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surfa ...
and speculates on how similar processes may work in
alien
Alien primarily refers to:
* Alien (law), a person in a country who is not a national of that country
** Enemy alien, the above in times of war
* Extraterrestrial life, life which does not originate from Earth
** Specifically, intelligent extrater ...
planetary system
A planetary system is a set of gravitationally
In physics, gravity () is a fundamental interaction which causes mutual attraction between all things with mass or energy. Gravity is, by far, the weakest of the four fundamental interacti ...
s.
The digital river
Dawkins begins the book by stating that all our ancestors reached adulthood and begot at least one child before they died. In a world where most organisms die before they can procreate, descendants are common but ancestors are rare. But we can all claim an unbroken chain of successful ancestors, right back to the first
single-celled organism
A unicellular organism, also known as a single-celled organism, is an organism that consists of a single cell, unlike a multicellular organism that consists of multiple cells. Organisms fall into two general categories: prokaryotic organisms an ...
.
If the success of an organism is measured by its ability to survive and reproduce, then all living organisms can be said to have inherited "good
gene
In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a ba ...
s" from successful ancestors. Each
generation
A generation refers to all of the people born and living at about the same time, regarded collectively. It can also be described as, "the average period, generally considered to be about 20–30 years, during which children are born and gr ...
of organisms is a sieve against which
replicated and
mutated
In biology, a mutation is an alteration in the nucleic acid sequence of the genome of an organism, virus, or extrachromosomal DNA. Viral genomes contain either DNA or RNA. Mutations result from errors during DNA or viral replication, mitos ...
genes are tested. Good genes fall through the sieve into the next generation while bad genes are removed. This explains why organisms become better and better at whatever it takes to succeed, and is in stark contrast to
Lamarckism
Lamarckism, also known as Lamarckian inheritance or neo-Lamarckism, is the notion that an organism can pass on to its offspring physical characteristics that the parent organism acquired through use or disuse during its lifetime. It is also calle ...
, which would require successful organisms to refine their genes during their lifetime.
Following this
gene-centered view of evolution
With gene defined as "not just one single physical bit of DNA utall replicas of a particular bit of DNA distributed throughout the world", the gene-centered view of evolution, gene's eye view, gene selection theory, or selfish gene theory hol ...
, it can be argued that an organism is no more than a temporary body in which a set of companion genes (actually
alleles
An allele (, ; ; modern formation from Greek ἄλλος ''állos'', "other") is a variation of the same sequence of nucleotides at the same place on a long DNA molecule, as described in leading textbooks on genetics and evolution.
::"The chro ...
) co-operate toward a common goal: to grow the organism into adulthood, before they go their separate ways in bodies of the organism's progeny. Bodies are created and discarded, but good genes live on as
replicas
A 1:1 replica is an exact copy of an object, made out of the same raw materials, whether a molecule, a work of art, or a commercial product. The term is also used for copies that closely resemble the original, without claiming to be identical. Al ...
of themselves, a result of a high-fidelity
copy process typical of
digital encoding.
Through
meiosis
Meiosis (; , since it is a reductional division) is a special type of cell division of germ cells in sexually-reproducing organisms that produces the gametes, such as sperm or egg cells. It involves two rounds of division that ultimately resu ...
(
sexual reproduction
Sexual reproduction is a type of reproduction that involves a complex life cycle in which a gamete ( haploid reproductive cells, such as a sperm or egg cell) with a single set of chromosomes combines with another gamete to produce a zygote tha ...
), genes share bodies with different companion genes in successive generations. Thus genes can be said to flow in a river through geological time. Even though genes are
selfish
Selfishness is being concerned excessively or exclusively, for oneself or one's own advantage, pleasure, or welfare, regardless of others.
Selfishness is the opposite of altruism or selflessness; and has also been contrasted (as by C. S. Lewis) w ...
, over the long run every gene needs to be compatible with all other genes in the
gene pool
The gene pool is the set of all genes, or genetic information, in any population, usually of a particular species.
Description
A large gene pool indicates extensive genetic diversity, which is associated with robust populations that can surv ...
of a population of organisms, to produce successful organisms.
A river of genes may fork, mostly due to the geographical separation between two populations of organisms. Because genes in the two branches never share the same bodies, they may
drift
Drift or Drifts may refer to:
Geography
* Drift or ford (crossing) of a river
* Drift, Kentucky, unincorporated community in the United States
* In Cornwall, England:
** Drift, Cornwall, village
** Drift Reservoir, associated with the village
...
apart until genes from the two branches become incompatible. Organisms created by these two branches form separate, non-
interbreeding
In biology, a hybrid is the offspring resulting from combining the qualities of two organisms of different breeds, varieties, species or genera through sexual reproduction. Hybrids are not always intermediates between their parents (such as in ...
species
In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...
, completing the process of
speciation
Speciation is the evolutionary process by which populations evolve to become distinct species. The biologist Orator F. Cook coined the term in 1906 for cladogenesis, the splitting of lineages, as opposed to anagenesis, phyletic evolution within ...
.
All Africa and her progenies
When tracing human
lineage
Lineage may refer to:
Science
* Lineage (anthropology), a group that can demonstrate its common descent from an apical ancestor or a direct line of descent from an ancestor
* Lineage (evolution), a temporal sequence of individuals, populati ...
back in time, most people look at parents, grandparents, great-grandparents and so on. The same approach is often taken when tracing descendants via children and grandchildren. Dawkins shows that this approach is misguided, as the numbers of ancestors and descendants seem to
grow exponentially as generations are added to the lineage tree. In just 80 generations, the number of ancestors can exceed a trillion trillion.
This simple calculation does not take into account the fact that every marriage is really a marriage between ''distant cousins'' which include second cousins, fourth cousins, sixteenth cousins and so on. The ancestry tree is not really a
tree
In botany, a tree is a perennial plant with an elongated stem, or trunk, usually supporting branches and leaves. In some usages, the definition of a tree may be narrower, including only woody plants with secondary growth, plants that are ...
, but a
graph
Graph may refer to:
Mathematics
*Graph (discrete mathematics), a structure made of vertices and edges
**Graph theory, the study of such graphs and their properties
*Graph (topology), a topological space resembling a graph in the sense of discre ...
.
Dawkins prefers to model ancestry in terms of genes flowing through a river of time. An ''ancestor gene'' flows down the river either as perfect replicas of itself or as slightly mutated ''descendant genes''. Dawkins fails to explicitly contrast ''ancestor organism'' and ''descendant organisms'' against ''ancestor genes'' and ''descendant genes'' in this chapter. But the first half of the chapter is really about differences between these two models of lineage. While organisms have ancestry graphs and progeny graphs via
sexual reproduction
Sexual reproduction is a type of reproduction that involves a complex life cycle in which a gamete ( haploid reproductive cells, such as a sperm or egg cell) with a single set of chromosomes combines with another gamete to produce a zygote tha ...
, a gene has a single chain of ancestors and a tree of descendants.
Given any gene in the body of an organism, we can trace a single chain of ''ancestor organisms'' back in time, following the lineage of this one gene, as stated in the
coalescent theory
Coalescent theory is a model of how alleles sampled from a population may have originated from a common ancestor. In the simplest case, coalescent theory assumes no recombination, no natural selection, and no gene flow or population structure, m ...
. Because a typical organism is built from tens of thousands of genes, there are numerous ways to trace the ancestry of organisms using this mechanism. But all these inheritance pathways share one common feature. If we start with all humans alive in 1995 and trace their ancestry by one particular gene (actually a
locus
Locus (plural loci) is Latin for "place". It may refer to:
Entertainment
* Locus (comics), a Marvel Comics mutant villainess, a member of the Mutant Liberation Front
* ''Locus'' (magazine), science fiction and fantasy magazine
** ''Locus Award' ...
), we find that the farther we move back in time, the smaller the number of ancestors become. The pool of ancestors continues to shrink until we find the ''
most recent common ancestor
In biology and genetic genealogy, the most recent common ancestor (MRCA), also known as the last common ancestor (LCA) or concestor, of a set of organisms is the most recent individual from which all the organisms of the set are descended. The ...
'' (MRCA) of all humans alive in 1995 ''via this particular gene pathway''.
In theory, one can also trace human ancestry via a single chromosome, as a chromosome contains a set of genes and is passed down from parents to children via
independent assortment
Mendelian inheritance (also known as Mendelism) is a type of biological inheritance following the principles originally proposed by Gregor Mendel in 1865 and 1866, re-discovered in 1900 by Hugo de Vries and Carl Correns, and later popularize ...
from only one of the two parents. But
genetic recombination
Genetic recombination (also known as genetic reshuffling) is the exchange of genetic material between different organisms which leads to production of offspring with combinations of traits that differ from those found in either parent. In eukaryo ...
(
chromosomal crossover
Chromosomal crossover, or crossing over, is the exchange of genetic material during sexual reproduction between two homologous chromosomes' non-sister chromatids that results in recombinant chromosomes. It is one of the final phases of geneti ...
) mixes genes from non-sister
chromatids
A chromatid (Greek ''khrōmat-'' 'color' + ''-id'') is one half of a duplicated chromosome. Before replication, one chromosome is composed of one DNA molecule. In replication, the DNA molecule is copied, and the two molecules are known as chro ...
from both parents during
meiosis
Meiosis (; , since it is a reductional division) is a special type of cell division of germ cells in sexually-reproducing organisms that produces the gametes, such as sperm or egg cells. It involves two rounds of division that ultimately resu ...
, thus muddling the ancestry path.
However, the
mitochondrial DNA
Mitochondrial DNA (mtDNA or mDNA) is the DNA located in mitochondria, cellular organelles within eukaryotic cells that convert chemical energy from food into a form that cells can use, such as adenosine triphosphate (ATP). Mitochondrial D ...
(mtDNA) is immune to sexual mixing, unlike the
nuclear DNA
Nuclear DNA (nDNA), or nuclear deoxyribonucleic acid, is the DNA contained within each cell nucleus of a eukaryotic organism. It encodes for the majority of the genome in eukaryotes, with mitochondrial DNA and plastid DNA coding for the rest. It ...
whose chromosomes are shuffled and recombined in
Mendelian inheritance
Mendelian inheritance (also known as Mendelism) is a type of biological inheritance following the principles originally proposed by Gregor Mendel in 1865 and 1866, re-discovered in 1900 by Hugo de Vries and Carl Correns, and later popularize ...
. Mitochondrial DNA, therefore, can be used to trace
matrilineal inheritance and to find the
Mitochondrial Eve
In human genetics, the Mitochondrial Eve (also ''mt-Eve, mt-MRCA'') is the matrilineal most recent common ancestor (MRCA) of all living humans. In other words, she is defined as the most recent woman from whom all living humans descend in an ...
(also known as the ''African Eve''), the most recent common ancestor of all humans via the mitochondrial DNA pathway.
Do good by stealth
The main themes of the third chapter are borrowed from Dawkins' own book, ''
The Blind Watchmaker
''The Blind Watchmaker: Why the Evidence of Evolution Reveals a Universe without Design'' is a 1986 book by Richard Dawkins, in which the author presents an explanation of, and argument for, the theory of evolution by means of natural selecti ...
''. This chapter shows how the gradual, continuous and cumulative enhancement to organisms via
natural selection
Natural selection is the differential survival and reproduction of individuals due to differences in phenotype. It is a key mechanism of evolution, the change in the heritable traits characteristic of a population over generations. Charle ...
is the only mechanism which can explain the complexity we observe all around us in nature. Dawkins adamantly refutes the ''"I cannot believe so and so could have evolved by natural selection"'' argument of
Creationists
Creationism is the religious belief that nature, and aspects such as the universe, Earth, life, and humans, originated with supernatural acts of divine creation. Gunn 2004, p. 9, "The ''Concise Oxford Dictionary'' says that creationism is 'th ...
, calling it the ''
Argument from Personal Incredulity''.
Creationists often claim that some features of organisms (e.g. resemblance of
Ophrys
The genus ''Ophrys'' is a large group of orchids from the alliance Orchis in the subtribe Orchidinae. They are widespread across much of Europe, North Africa, Caucasus, the Canary Islands, and the Middle East as far east as Turkmenistan.
These ...
(
orchid
Orchids are plants that belong to the family Orchidaceae (), a diverse and widespread group of flowering plants with blooms that are often colourful and fragrant.
Along with the Asteraceae, they are one of the two largest families of flowering ...
) to female wasp,
figure-eight dances of
honeybee
A honey bee (also spelled honeybee) is a eusocial flying insect within the genus ''Apis'' of the bee clade, all native to Afro-Eurasia. After bees spread naturally throughout Africa and Eurasia, humans became responsible for the current cosmo ...
s, mimicry of
stick insect
The Phasmatodea (also known as Phasmida, Phasmatoptera or Spectra) are an order of insects whose members are variously known as stick insects, stick-bugs, walking sticks, stick animals, or bug sticks. They are also occasionally referred to as ...
s, etc.) are too complicated to be a result of evolution. Some say, ''"half of an X will not work at all."'' Others say, ''"in order for X to work, it had to be perfect the first time."'' Dawkins concludes that these are no more than bold assertions based on ignorance:
... Do you actually know the first thing about orchids, or wasps, or the eyes with which wasps look at females and orchids? What emboldens you to assert that wasps are so hard to fool that the orchid's resemblance would have to be perfect in all dimensions in order to work?
Dawkins goes on to illustrate his point by demonstrating how scientists have been able to fool creatures big and small using seemingly dumb triggers. For instance,
stickleback
The sticklebacks are a family of ray-finned fishes, the Gasterosteidae which have a Holarctic distribution in fresh, brackish and marine waters. They were thought to be related to the pipefish and seahorses but are now thought to be more closel ...
fish treat a pear-shape as a sex bomb (a
supernormal stimulus). Gulls' hard-wired
instinct
Instinct is the inherent inclination of a living organism towards a particular complex behaviour, containing both innate (inborn) and learned elements. The simplest example of an instinctive behaviour is a fixed action pattern (FAP), in which a v ...
s make them reach over and roll back not just their own stray eggs, but also wooden cylinders and cocoa tins. Honeybees push out their live and protesting companion from their hive, when the companion is painted with a drop of
oleic acid
Oleic acid is a fatty acid that occurs naturally in various animal and vegetable fats and oils. It is an odorless, colorless oil, although commercial samples may be yellowish. In chemical terms, oleic acid is classified as a monounsaturated omega ...
. Furthermore, a turkey will kill anything which moves in its nest unless it cries like a baby turkey. If the turkey is deaf, it will mercilessly kill its own babies.
As part of this, Dawkins emphasises the gradual nature of evolution. For example, some creatures such as the
stick insect
The Phasmatodea (also known as Phasmida, Phasmatoptera or Spectra) are an order of insects whose members are variously known as stick insects, stick-bugs, walking sticks, stick animals, or bug sticks. They are also occasionally referred to as ...
s possess the most amazing degree of
camouflage
Camouflage is the use of any combination of materials, coloration, or illumination for concealment, either by making animals or objects hard to see, or by disguising them as something else. Examples include the leopard's spotted coat, the ...
, but in fact any sort of camouflage is better than none. There is a
gradient
In vector calculus, the gradient of a scalar-valued differentiable function of several variables is the vector field (or vector-valued function) \nabla f whose value at a point p is the "direction and rate of fastest increase". If the gradi ...
from perfect camouflage to zero camouflage. A 100 percent camouflage is better than 99 percent. A 50 percent camouflage is better than 49 percent. A 1 percent camouflage is better than no camouflage. A creature with 1 percent better camouflage than its contemporaries will leave more descendants over time (an evolutionary success), and its good genes will come to dominate the gene pool.
Not only can we classify the degree of insect camouflage using a gradient, we can also study all aspects of the surrounding environment as gradients. For instance, a 1 percent camouflage may not be distinguishable from no camouflage under bright daylight. But as light fades and night sets in, there is a critical moment when the 1 percent camouflage helps an insect escape detection by its predator, while its companion with no camouflage is eaten. The same principle can be applied to the distance between prey and predator, to the angle of view, to the skill or the age of a creature, etc.
In addition to demonstrating how gradual changes can bring about features as complex as the
human eye
The human eye is a sensory organ, part of the sensory nervous system, that reacts to visible light and allows humans to use visual information for various purposes including seeing things, keeping balance, and maintaining circadian rhythm.
...
, Dawkins states that
computer simulation
Computer simulation is the process of mathematical modelling, performed on a computer, which is designed to predict the behaviour of, or the outcome of, a real-world or physical system. The reliability of some mathematical models can be dete ...
work by Swedish scientists Dan Nilsson and Susanne Pelger (although it is not a computer simulation but simple mathematical model) shows that the eye could have evolved from scratch a thousand times in succession in any animal lineage. In Dawkins' own words, "the time needed for the evolution of the eye... turned out to be too short for geologists to measure! It is a geological blink." And, "it is no wonder ''the'' eye has evolved at least forty times independently around the animal kingdom."
God's utility function
This chapter is Dawkins's take on the ''
meaning of life
The meaning of life, or the answer to the question: "What is the meaning of life?", pertains to the significance of living or existence in general. Many other related questions include: "Why are we here?", "What is life all about?", or "What ...
'' or the ''purpose of life''.
Dawkins quotes how
Charles Darwin
Charles Robert Darwin ( ; 12 February 1809 – 19 April 1882) was an English naturalist, geologist, and biologist, widely known for his contributions to evolutionary biology. His proposition that all species of life have descended fr ...
lost his faith in religion, "I cannot persuade myself that a
beneficent and
omnipotent
Omnipotence is the quality of having unlimited power. Monotheistic religions generally attribute omnipotence only to the deity of their faith. In the monotheistic religious philosophy of Abrahamic religions, omnipotence is often listed as one ...
God would have designedly created the
Ichneumonidae
The Ichneumonidae, also known as the ichneumon wasps, Darwin wasps, or ichneumonids, are a family (biology), family of parasitoid wasps of the insect order Hymenoptera. They are one of the most diverse groups within the Hymenoptera with roughly 2 ...
with the express intention of their feeding within the living bodies of
Caterpillars
Caterpillars ( ) are the larval stage of members of the order Lepidoptera (the insect order comprising butterflies and moths).
As with most common names, the application of the word is arbitrary, since the larvae of sawflies (suborder Symp ...
." We ask ''why'' a caterpillar should suffer such cruel punishment. We ask ''why''
digger wasps couldn't first kill caterpillars to save them from a prolonged and agonising torture. We ask ''why'' a child should die an untimely death. And we ask ''why'' we should all
grow old and die.
Dawkins rephrases the word ''purpose'' in terms of what economists call a
utility function
As a topic of economics, utility is used to model worth or value. Its usage has evolved significantly over time. The term was introduced initially as a measure of pleasure or happiness as part of the theory of utilitarianism by moral philosopher ...
, meaning ''"that which is maximised"''. Engineers often investigate the intended purpose (or utility function) of a piece of equipment using
reverse engineering
Reverse engineering (also known as backwards engineering or back engineering) is a process or method through which one attempts to understand through deductive reasoning how a previously made device, process, system, or piece of software accompli ...
. Dawkins uses this technique to reverse-engineer the purpose in the mind of the Divine Engineer of Nature, or the ''Utility Function of God''.
According to Dawkins, it is a mistake to assume that an
ecosystem
An ecosystem (or ecological system) consists of all the organisms and the physical environment with which they interact. These biotic and abiotic components are linked together through nutrient cycles and energy flows. Energy enters the syste ...
or a
species
In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...
as a whole exists for a purpose. In fact, it is wrong to suppose that individual organisms lead a meaningful life either. In nature, only genes have a utility function – to perpetuate their own existence with indifference to great sufferings inflicted upon the organisms they build, exploit and discard. As hinted at in chapter one, genes are the supreme lords of the natural world. In other words, the
unit of selection
A unit of selection is a biological entity within the hierarchy of biological organization (for example, an entity such as: a self-replicating molecule, a gene, a cell, an organism, a group, or a species) that is subject to natural selection. ...
is the gene, not an individual, or any other higher-order group as championed by proponents of
group selection
Group selection is a proposed mechanism of evolution in which natural selection acts at the level of the group, instead of at the level of the individual or gene.
Early authors such as V. C. Wynne-Edwards and Konrad Lorenz argued that the behav ...
.
As long as an organism survives its childhood and manages to reproduce thus passing its genes down to the next generation, what happens to the parent organism afterwards does not really bother genes. Because an organism is always at the danger of dying from accidents (a waste of investment), it pays for the genes to build an organism which pools almost all its resources to produce offspring as early as possible. Thus we accumulate damages to our body as we age and harbour late-onset diseases such as
Huntington's disease
Huntington's disease (HD), also known as Huntington's chorea, is a neurodegenerative disease that is mostly inherited. The earliest symptoms are often subtle problems with mood or mental abilities. A general lack of coordination and an unst ...
which have minimum impact on the evolutionary success of our gene overlords.
Genes, Dawkins argues, are indifferent to who or what gets hurt, so long as DNA is passed on. He concludes:
During the minute it takes me to compose this sentence, thousands of animals are being eaten alive; others are running for their lives, whimpering with fear; others are being slowly devoured from within by rasping parasites; thousands of all kinds are dying from starvation, thirst and disease. It must be so. If there is ever a time of plenty, this very fact will automatically lead to an increase in population until the natural state of starvation and misery is restored.
The replication bomb
In the last chapter, Dawkins considers how Darwinian evolution may look outside
planet Earth
Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surface ...
. It seems that the trigger event would be the spontaneous arising of
self-replicating entities or the phenomenon of
heredity
Heredity, also called inheritance or biological inheritance, is the passing on of traits from parents to their offspring; either through asexual reproduction or sexual reproduction, the offspring cells or organisms acquire the genetic inform ...
. Once this process is initiated, it will launch an explosion of replicating entities until all available resources are used and all vacant niches are taken. Thus the title of the chapter.
Dawkins tries to distill ten milestones from the history of the only one replication bomb we know of, life on Earth. He strips any ''local conditions'' peculiar to Earth from these milestones which he calls ''thresholds'', in the hope that these ''thresholds'' will be applicable to an alien evolution in an
alien
Alien primarily refers to:
* Alien (law), a person in a country who is not a national of that country
** Enemy alien, the above in times of war
* Extraterrestrial life, life which does not originate from Earth
** Specifically, intelligent extrater ...
planetary system
A planetary system is a set of gravitationally
In physics, gravity () is a fundamental interaction which causes mutual attraction between all things with mass or energy. Gravity is, by far, the weakest of the four fundamental interacti ...
.
From the starting point of the ''Replicator Threshold'', we may eventually reach the higher thresholds of ''Consciousness'', ''Language'', ''Technology'', and ''Radio''. The final threshold is ''Space Travel''. In
reaching the moon, we have hardly made it past the front door.
References
External links
{{Portal bar, Evolutionary biology, Books
1995 non-fiction books
Basic Books books
Books about evolution
Books by Richard Dawkins
English-language books
Genetic genealogy