MENDEL’S LAWS OF INHERITANCE Vs HUMAN EVOLUTION :
The origin of Man, or the Beginning of Man as a new form of Life may have a basis that lies outside operation of natural causes. To make transition from an old species to a new species which is often called ‘EVOLUTION’, the breeding interactions of species involved must operate according to the Laws of Inheritance discovered by Gregor Johann Mendel, the Father of Genetics. In this article, I would like to describe the Laws of Inheritance and the problems that I encounter to verify The Theory of Evolution while using the Mendelian Principles of Heredity and Variation.
Gregor Johann Mendel(1822-1884), Austrian monk noted for his experimental work on Heredity. At the Augustinian monastery in Brno(1843-1868) he conducted experiments chiefly on Garden Peas(Pisum sativum) using a controlled pollination technique and a careful statistical analysis of his results. He produced the first accurate and scientific explanation of ‘Hybridization’. Some evolutionary geneticists and evolutionary anthropology scholars have shared opinions claiming that the ‘hybridization’ of unknown, ancestral Homo sapiens with other species of the genus Homo such as Neanderthals, and Denisova hominids may have resulted in production of anatomically modern humans(Homo sapiens sapiens). Their views on blending of hereditary factors is not supported by Mendel’s classic experiments in Hybridization. According to Mendel, inheritance is particulate. Distinct genetic factors combine to produce a certain somatic result without losing their separate identities. They can therefore be reassorted and enter into new genetic combinations in the next generation. The hypothesis of Hybridized Anatomically Modern(HAM) humans is fundamentally inconsistent with the Laws of Inheritance discovered by Mendel. If modern man is a product of Hybridization, the present, surviving human population would include a few surviving members of Neanderthals, Denisova, and other ancestral hominids who successfully reproduced with an unknown, ancestral Homo sapiens species which got transformed into ‘HAM’ humans.
THE LAW OF BIOGENESIS AND THE LAW OF NATURAL GENERATION :
The term ‘Generation’ means to produce offspring. The term ‘Propagation’ means to transmit hereditary characteristics by reproduction. The Law of Biogenesis states the Principle that living organisms originate only from other living organisms closely similar to themselves. It is ‘The Law of Like Generating Like’. A species always breeds true to its own species. Its members always generate organisms which are classified as belonging to the same species, however much they vary among themselves as individuals within the group. The sub-groups, the races, or varieties of species are able to breed with one another, but diverse species cannot interbreed. By the Law of Natural Generation, offspring will always be of the same species as the parent organism. Hence, species is self-perpetuating and maintain stability of all other groupings like the genera, phyla, and families which remain as fixed from generation to generation. In Plant and Animal Kingdom, a species distinguishes itself by its ability to maintain its stability from generation to generation. The Mendelian System of Heredity states that an inherited characteristic is determined by the combination of two hereditary units(now called genes), one from each of the parental reproductive cells or gametes(Sperm and Egg Cell). The term genome describes the set of genes characteristic of each species. Every human being arrives on planet Earth with an original, unique, distinctive, and one of its own kind of genome that has never, ever existed in the past, and would never exist again in the future. Sexual reproduction is a creative process which involves a type of cell division called ‘MEIOSIS’ that results in production of Sperm or Egg Cell. The fertilization of egg cell by sperm always creates a new kind of genome.
THE ORIGIN OR THE BEGINNING OF ANATOMICALLY MODERN HUMANS:
To explain the Origin of Man, The Beginning of Man on the basis of Theory of Evolution, demands presence of two, identical, rare, mutant individuals(a male, and a female) to produce offspring and to establish an entirely new, modern human population in the geographical regions of the Old World. About 30, 000 years ago, modern humans may have shared the planet with Neanderthals and other hominid species. Techniques of DNA extraction and genomic sequencing have advanced and find application in the understanding of the genus Homo. The claims about Hybridization of archaic humans such as Neanderthals with Homo sapiens finds support from DNA studies of the current, surviving members of human population but those shared genetic traits are not of major significance and do not account for the morphological appearance of the interbreeding species. At the same time, it may be noted that 30 – 35, 000 years ago, Neanderthals disappeared from the fossil record. Similarly, Hominid Denisova, discovered in Altai Mountains, Southern Siberia lived 41, 000 years ago. Homo sapiens floresiensis(Flores Man) suddenly disappeared 12, 000 years ago. Hominid Red Deer discovered in China lived 14.5 to 11.5 thousand years ago. To make a credible claim about interbreeding between Neanderthals and Homo sapiens, we need to demonstrate presence of traits characteristic of Homo sapiens in the DNA extracted from Neanderthal fossil specimens. It will be correct to claim that from Holocene Epoch or Series, approximately for the last 10, 000 years, modern humans constitute the only surviving members of the Hominid Family found on planet Earth.
Charles Darwin uses the term species to signify “a set of individuals closely resembling each other” – a class of plants or animals having certain characteristics. The French naturalist George Louis Leclerc Comte de Buffon(1707-1788) in his monumental compendium on Natural History(Histoire Naturelle General et Particuliere, 44 Volumes, 1749-1804) described man as a zoological species. Buffon determined species not by their physical appearances but by their reproductive history. Two individual animals or plants are of the same species if they can produce fertile offspring. According to Buffon, a species is known only through the history of its propagation. Buffon opened the way to development of Paleontology to discover lost species. The status of Anatomically Modern Humans as a distinct species is verified as human populations consist of members that are genetically similar, interbreeding or potentially interbreeding individuals that share the same collection of inherited characteristics, whose combination is unique to our species. But, diverse species cannot interbreed. Organisms different in species cannot reproduce productively and if crossbred, like the horse and the ass, they produce a sterile hybrid like the mule. Hybrid is the term for the offspring of a cross between two different subspecies or species. In Genetics, hybrid is the term for the offspring of parents differing in any genetic characteristic. If Neanderthal is one of the parents of Anatomically Modern Humans, identity of the second Hominid parent has to be ascertained, and the characteristics of that parent are accounted for using Mendel’s Laws of Inheritance.
The concept of Hybridized Anatomically Modern(HAM) humans cannot be verified in absence of any surviving members of Neanderthal, Denisova, or other Hominid population with whom modern man may have reproduced 30 to 40, 000 years ago.
MENDEL’S LAWS OF INHERITANCE :
Mendel demonstrated the inheritance patterns through breeding experimentations. He discovered in 1866 hereditary factors or “genes” whose existence he deduced without seeing them. Mendel’s statistical analysis of his data provided the mathematical basis for modern Genetics. There are four principles of hereditary phenomenon discovered and formulated by Mendel :
1. The Law of Independent Unit Characters which states that characters such as height, color, etc., are inherited separately as Units,
2. The Law of Segregation which states that body cells and primordial germ cells contain pairs of such Unit Characters and that when gametes(Sperm or Egg Cell) are produced, each gamete receives only one member of each such pair,
3. The Law of Dominance which states that in every individual there is a pair of determining factors for each Unit Character, one from each parent, if these factors are different(heterozygous), one Character( the Dominant) appears in the organism, the other( Recessive) being latent; the Recessive Character can appear in the organism only when the Dominant is absent; hence in all crossbred generations, Unit Characters are shown in varying combinations, each appearing in a definite proportion of the total number of offspring, and
4. The Law of Independent Assortment which states that any one pair of Characters is inherited independently, not withstanding the simultaneous transmission of other traits. This Law is modified by the discovery of Linkage and Pleiotropy. Linkage describes the tendency of some genes to remain together and act as a Unit or Linkage Group. In Inheritance, the Linkage Group of genes are generally found in the same chromosome. Pleiotropy is the condition in which a single gene exerts simultaneous effects on more than one character in the offspring.
ABOUT GENETICS AND THE CONSTANCY OF GENETIC CODE :
Genetics is an important aspect of many areas of Biology. Genetics helps in the study and identification of specific types of organisms; research in Molecular Genetics involves studies on chemical structure and functions of genes at molecular level; Cyto Genetics studies location of genetic material in cells and the role of genes in cell division; Developmental Genetics studies the genetic function in embryological phenomena; Behavior Genetics studies the role of gene in regulating behavior; Population Genetics studies genetics in relation to the “evolutionary” process. Medical Genetics involves application of genetic principles to the practice of Medicine such as the study of inheritance of diseases in families. Genetic factors cause many health disorders affecting man. Some human diseases are entirely genetic in origin and environmental factors play little if any part. This group of genetic disorders includes chromosomal abnormalities, and so-called “Unifactorial Disorders” which are due to single gene defects or Mendelian factors. There are over 3 thousand of such unifactorial disorders. The mode of inheritance of such disorders is straight forward and follows Mendelian Principles. Mendel’s Laws of Inheritance have their practical applications in Medical Genetics. However, the use of Mendel’s Principles in Population Genetics to verify The Theory of Evolution is highly controversial because of the speculative postulates about transformation of old species into a new species . Several single-celled Blue-Green algae, plankton, microbes, viruses, protozoans, insects, crocodiles, turtles, sharks and other organisms are known to be existing upon Earth from billions to several millions of years. The unchanging genetic code in all past and present members of these long-lived species permit the genes to have the same effects on their carriers from generation to generation. Because of constancy of the genetic code, we can identify existence of individual species which maintain their species-specific traits as per Mendelian Principles.
While describing Genetics as the area of Biology concerned with the study of inheritance, the process by which certain characteristics or traits of organisms are handed down from parent to offspring, I would like to suggest that a creative mechanism, a creative process or a creative operation could be at work when Genetics accounts for variations in similar or related animals and plants. I would like to emphasize the fact of all organisms existing as Individuals with Individuality. In Nature, living things have no choice other than that of existence as Individuals with Individuality. Even a mob of genetically identical(“CLONES”) colony of bacteria of E. coli are experimentally proved to behave as Individuals with Individuality.
In higher organisms with cells that contain a Nucleus, the genetic material called DNA(deoxyribonucleic acid) is carried by structures known as Chromosomes in the Nucleus, and the cytoplasmic structures known as Mitochondria. The genetic material called RNA(ribonucleic acid) is found in the Nucleolus(present inside the Nucleus) and structures called Ribosomes found in the Cytoplasm.
The Ribosomes are the sites of protein synthesis present in the Cytoplasm. DNA interacts with ‘transfer RNA'(t-RNA), ‘Messenger RNA'(m-RNA), and Ribosomal RNA in the process of protein synthesis. The Chromosome is divided into Units called Genes. Each Gene is responsible for a particular trait and hence Gene is the Unit of inheritance. The term ‘allele’ describes either of a pair of genes at the same position on both members of a pair of chromosomes and conveying traits that are inherited by Mendelian Laws.There could be small chemical differences in genes that are expressed as different versions of the same trait (‘alleles’). Each gene is responsible for the manufacture of a particular protein which is involved in development of a trait associated with it. Each chromosome of each species of higher organisms has a definite number and arrangement of genes which govern the structure and functions of the cells. It is important to note that, while genes are located inside the Nucleus of the cell, the actual protein synthesis occurs in structures called Ribosomes present in the Cytoplasm outside the Nucleus. While we appreciate the role of genes as Units of Inheritance, we should give equal importance to the Living Substance, the Living Material, or the Living Matter called Cytoplasm that is found inside the living cells, outside the Nucleus of the cell. There are basically three classes of Genes: 1. Structural genes which determine the sequences of amino acids that go to makeup proteins or the smaller chain of molecules known as polypeptides, 2. Coding genes which specify molecules that function in the processes involved in protein synthesis, and 3. Regulatory genes which are called Noncoding genes for they act solely as “Recognition” sites for enzymes and other proteins involved in controlling protein synthesis.
THE GENETIC CODE AND THE ROLE OF MUTATIONS:
MENDEL’S LAWS OF INHERITANCE VS HUMAN EVOLUTION : GENETIC CODE DESCRIBES THE RELATIONSHIP BETWEEN THE COMPOSITION OF DNA AND THAT OF PROTEINS PRODUCED BY GENES .
The Genetic Code describes the relationship between composition of DNA and that of proteins produced by genes. Genetic Code is the chemical equation by which hereditary information is translated from genes into proteins. Changes in the genetic code are called Mutations. Mutations can cause a change in protein synthesis. In higher organisms, when mutation involves the germ-line cells that eventually develop into sperm or egg cells, the mutation and its consequence of altered protein synthesis is inherited by offspring. A mutation can be minor and relatively insignificant, or it can cause serious deformity or metabolic deficiency in the organism. Most mutations tend to be harmful. Fortunately, a typical gene in higher organisms is segmented and the entire genetic information of a gene is not contained in a single, unbroken strand of DNA molecule. The value of having the genetic code in segments is to reduce the chances of mutations causing harmful changes in protein synthesis. Certain self-repair mechanisms also exist to deal with the damage done to DNA. Very often, the damaged DNA is repaired or the cell carrying the damaged DNA is killed and destroyed. For this reason, it is important to recognize the simple fact of DNA damage associated with mutations irrespective of its cause. The Theory of Evolution proposes that random, unguided, and apparently purposeless mutations lead to gradual changes in a species and eventually lead to its descent as a new species. As per the Theory of Evolution, mutations may bring about three kinds of changes; 1. Changes in the morphological appearance of an organism, 2. Changes in the skeletal and other anatomical structures of an organism, and 3. Changes in the behavior displayed by an organism.
In higher organisms, the cells are differentiated to perform special functions. For example, muscle cells have ability of contraction. This physiological function of contraction is easily demonstrated by applying an electrical stimulus to muscle as done in Muscle Twitch in Frog Experiment. Animals have different abilities of locomotion; some crawl or creep, or slide on a surface, some swim, or move in water, some fly or glide in air, and others walk, run, climb, and swing in a variety of amazing manners. Whatever may be the mode of locomotion, all animal muscle cells display the same physiological function of contraction. While the physiology remains the same, the muscles of each animal species display individualistic functional characteristics. For mutations are random, unguided, and purposeless, they cannot account for guided, sequential and purposeful nature of muscle contractions which have several creative applications in the natural world.
MENDEL’S LAWS OF INHERITANCE AND THE MISSING LINK :
The above image reveals a fundamental problem faced by The Theory of Evolution when it attempts to account for Human Evolution. No extinct or living species is able to bridge the gap between modern man(Homo sapiens sapiens) and his nearest allies among Hominid Family and other Primates such as Chimpanzee and Gorilla.
Senckenberg Natural History Museum, Frankfurt, Germany prepared replicas of Hominid species using the fossils discovered at different geographical locations. Sahelanthropus tchadensis lived 6.8 million years ago. It is one of the oldest Hominid specimens, found in 2003 in Djurab desert in Chad, Africa.
Australopithecus afarensis discovered in Afar region of Ethiopia, Africa in 1975. This Hominid lived 3.2 million years ago.
Australopithecus africanus ,this Hominid replica nicknamed “Mrs Ples” lived 2.5 million years ago. Discovered in 1947, at Sterfontein, South Africa.
Paranthropus aethiopicus lived 2.5 million years ago. Discovered near Lake Turkana in Kenya, Africa, in 1985.
Paranthropus boisei, nicknamed “Zinz” lived 1.8 million years ago. Discovered in 1959 in the Olduvai Gorge of Tanzania, Africa.
Homo Rudolfensis lived about 1.8 million years ago. Discovered in 1972 in Koobi Fora, Kenya, Africa.
“TURKANA BOY” Homo ergaster lived about 1.5 million years ago. Initially thought to be an important “missing link” in Human Evolution.
Homo heidelbergensis or Homo rhodesiensis. This replica is made from the fossils found in Sima de los Huesos, Spain in 1993. He lived about 500,000 to 350,000 years ago. Fossils also found in other places like Italy, France, and Greece. Homo sapiens may have appeared 300,000 years ago. Heidelbergensis could be the ancestor of Neanderthals which is a subspecies of Sapiens species.
Homo erectus lived 1, 500, 000 to 300, 000 years ago.
Pithecanthropus, “JAVA MAN” discovered in 1891 could be the first to use fire. He used stone tools and belongs to the Lower Pleistocene Period.
It could be of interest to note that Rhodesian Man( Heidelberg Man – Germany) had a large, thick skull, a sloping forehead, a chinless jaw, a brain larger than that of modern man. The height was about five feet(152 cm) or slightly over.
Sinanthropus, Homo erectus pekinensis, or PEKING MAN belonged to the Middle Pleistocene.
Homo sapiens neanderthalensis lived 56,000 years ago. The above is the replica nicknamed “OLD MAN OF LA CHAPELLE” found near La Chapelle aux-Saints in France in 1908.
Homo sapiens floresiensis, the FLORES MAN discovered in Liang Bua Cave, Flores, Indonesia in 2003. Lived about 18,000 years ago.
It could be of interest to note that Flores Man was only about 3 feet in height. Initially thought to be a subspecies of Sapiens and now considered as a separate species. This Hominid species disappeared without any trace for unknown reasons.
The above is a replica of Homo sapiens found in a cave in Israel in 1969. He lived between 100,000 to 90, 000 years ago. It is important to note that it is not representative of true, modern humans called Homo sapiens sapiens.
Homo sapiens idaltu lived about 160, 000 years ago in Pleistocene Period(Middle Paleolithic), in Ethiopia, Africa, may mark the origin of anatomically modern Homo sapiens, making distinction between Homo erectus species and Homo sapiens species. They were at the threshold of modern anatomy but not fully modern humans.
Homo sapiens Red Deer represents “Red Deer Cave” people who lived 11, 500 to 14, 500 years ago in Maludong, Yunnan Province, Southern China. Red Deer Man had high domed braincase, small eyebrow ridges, lower jaw ended in a prominent chin, with a body less muscular than those of earlier Hominids.