All living organisms have the capacity to produce new organisms similar to themselves. The methods and complexity of the reproductive process vary tremendously, but there are two fundamental types: asexual reproduction, in which a single organism separates into two or more equal or unequal parts; and sexual reproduction, in which a pair of specialized sex cells fuse .
Asexual reproduction is found in the majority of living organisms, including most plants, protists (e.g. bacteria, protozoans, and unicellular algae and fungi), and many lower invertebrates. In unicellular organisms it usually takes the form of fission (or mitosis), in which the parent organism splits into two or more identical ‘daughter’ organisms. In some cases, the cells thus formed may remain clustered together to form filaments or colonies. Protozoans and many lower plants (e.g. ferns) propagate by shedding spores – reproductive cells that produce new organisms without fertilization. In some lower animals (e.g. hydra) and in yeasts, a common form of reproduction is budding: a small protuberance or bud forms on the surface of the parent’s body, increases in size, and finally separates and develops into a new individual identical with the parent. Sponges produce internal buds known as gemmules.
Regeneration is a specialized form of asexual reproduction. Some organisms (e.g. starfish, polyps, zebrafish, flatworms, newts, and salamanders) can regenerate new heads, limbs, internal organs, or other body parts if the originals are lost or injured. Many plants are capable of total regeneration, i.e. the formation of a whole individual from a single fragment such as a stem, root, leaf, or even a small slip from such an organ (as in grafting). Among animals, the lower the form, the more capable it is of total regeneration; no vertebrates have this power, though clones of mammals have been produced in the laboratory from single somatic cells (the first clone – Dolly the sheep – was produced in 1997). Regeneration is closely allied to vegetative reproduction, the formation of a new individual by various parts of the organism not specialized for reproduction. The highest animals that exhibit vegetative reproduction are the colonial tunicates (e.g. sea squirts), which, much like plants, send out runners in the form of stolons, small parts of which form buds that develop into new individuals.
Sexual reproduction occurs in many unicellular organisms and in all multicellular plants and animals. In higher invertebrates and in all vertebrates it is the exclusive form of reproduction, except in the few cases in which parthenogenesis (virginal reproduction) is also possible. A number of unicellular organisms multiply by a primitive form of sexual reproduction known as conjugation: two similar organisms fuse, exchange nuclear materials, and then break apart; each organism then reproduces by fission.
Most multicellular animals and plants undergo a more complex form of sexual reproduction in which distinct male and female reproductive cells (gametes) unite to form a single cell, known as a zygote, which then undergoes successive divisions to form a new organism. In this type of sexual reproduction, half the genes in the zygote come from one parent and half from the other. Whereas asexual reproduction allows beneficial combinations of characteristics to continue unchanged, offspring produced by sexual reproduction inherit endlessly varied combinations of characteristics.
In the case of plants, wind and insects carry the sperm to the stationary egg, or, in a liquid medium, the sperm swims to the egg. In lower animals, sperm and eggs are often deposited in water, but this method is haphazard as only a few of the many sperm discharged reach the eggs. In higher animals, the spermatozoa, contained in the seminal fluid, are deposited in the lower segment of the female reproductive tract. All mammals, reptiles, and birds as well as some invertebrates, including snails, worms, and insects, use internal fertilization. In many lower multicellular organisms and all higher plants, a sexually produced generation alternates with an asexually produced generation.
After fertilization of the egg, the resulting zygote undergoes cell division and differentiation to form the embryo. In most higher plants, the embryo is enclosed in a layer of nutritive material surrounded by a hard outer covering, forming the seed. In most lower animals, the embryo, surrounded by the nutritive material of the former ovum, is enveloped by a leathery or calcareous shell and is extruded from the body of the female. Oviparous animals, such as birds, lay their eggs before the young are completely developed. Ovoviviparous animals produce eggs in shells that hatch within the mother’s body. Placental mammals are viviparous, i.e. they give birth to live young without forming shelled eggs; the embryo is implanted in the uterus and nourished by the mother until almost completely developed.
Parthenogenesis involves the development of an ovum without fertilization. It is common among lower plants and invertebrate animals, especially rotifers, aphids (plant lice), ants, wasps, and bees. In the aphids there is an alternation of generations: parthenogenetic development of eggs (while in the oviduct) takes place in summer when conditions are favourable, while with the coming of autumn, with lack of sunshine and less abundant food, males appear together with sexual reproduction. The same sex cells sometimes produce different kinds of individuals according to whether or not they are fertilized. For instance, among our common honey bees, a male individual (a drone) arises out of the eggs of the queen if the egg has not been fertilized, and a female (a queen or working bee) if it has. A few kinds of amphibians, reptiles, and birds can reproduce parthenogenetically.
Hermaphroditism refers to the presence of organs producing sperm and ova in the same individual. It occurs in the great majority of flowering plants. Most hermaphroditic plants produce male and female elements at different times to ensure cross-pollination, but a few, such as the violet and the evening primrose, are self-pollinated. Hermaphroditism habitually occurs in many invertebrate animals, in the hagfish and tunicate, and a genus of sea bass. It occurs occasionally in other fishes, and in frogs, toads, and certain newts among the amphibians. Hermaphrodite animals are rarely self-fertilizing; in most cases the spermatozoa and ova mature at different times, or the male and female external organs are located so that self-fertilization is impossible. Among the invertebrates, sponges, coelenterates, some mollusks, and earthworms are regularly hermaphroditic. Flatworms have a complete set of male and female gonads in each segment and regularly fertilize themselves.
True functional hermaphroditism is rare or absent in higher animals. Animals intermediate in form between males and females occasionally appear, but they are usually sterile, and, when fertile, do not produce both fertile eggs and fertile sperm. Such individuals are often called intersexes. Intersex humans also appear; this category includes all people born with sex chromosomes, external genitalia, or internal reproductive systems that are not considered standard for male or female.
Although scientists can now describe the physical processes involved in reproduction in great detail, fertilization remains one of the least understood of all fundamental biological processes. The mechanisms involved in parthenogenesis are not understood either. And the seemingly miraculous process whereby a fertilized egg develops into a full-grown organism raises even more questions. Genes do not explain this complex process, as they carry instructions for making proteins, but not for their arrangement into tissues, organs, etc. Something else appears to guide and coordinate embryological development. According to occult science, physical processes are organized and guided from subtler, nonphysical levels of an organism’s constitution, visible only to those who have developed higher clairvoyance .
Explaining how and why sex emerged in the first place poses insuperable problems for orthodox evolutionary theory. The idea that all the intricate components of the male and female reproductive systems could emerge more or less simultaneously, in perfect working order, through purely random genetic mutations, is utterly absurd. Moreover, in the darwinian struggle to pass on more of one’s genes to future generations, asexuality is twice as efficient as sexuality. This is because an asexual parent transmits all its genes to each progeny, whereas when a sexual organism forms sperm or egg cells, half the genes are removed. As Richard Dawkins puts it: ‘Sexual reproduction is analogous to a roulette game in which the player throws away half his chips at each spin. … [T]he existence of sexual reproduction really is a huge paradox.’ Another darwinist says that sex ‘does not merely reduce fitness, but halves it’, and should therefore be ‘powerfully selected against and rapidly eliminated wherever it appears’ .
Sexual organisms face various problems that are avoided in asexual organisms. In addition to the cost of evolving and maintaining the sex organs, there is the possibility of blood Rh factor incompatibilities and tissue rejection between mother and child. Because sperm and eggs are like foreign tissue due to their different genetic makeup, special mechanisms are required to keep the body’s immune defences from destroying its own gametes. Finding a mate, courting, and copulating involve risks that place sexual organisms at a further disadvantage compared with asexual organisms. Scientists therefore admit that ‘there is no convincing Darwinian history for the emergence of sexual reproduction’.
In the case of asexual organisms, all offspring are essentially clones of the single parent, and differ from it only by new mutations. Sex, on the other hand, creates diversity. Sex shreds every genome in every generation, with the result that all offspring are genetically different (except in rare cases such as identical twins). Scientists acknowledge that it is difficult to identify any short-term individual benefit in diversity. They also believe that sex would tend to slow the evolution of a species rather than accelerate it, because it breaks up gene combinations with no regard for their adaptive value.
Another hypothesis is that the benefit of sex lies not in accelerating the spread of beneficial mutations but in more rapidly eliminating harmful mutations. Asexual lineages can acquire more harmful mutations but never less, whereas in a sexual population it is possible for offspring to have fewer harmful mutations than either parent. The problem with this argument is that darwinism assumes that evolution cannot look ahead to the future; it can only select traits based on their immediate short-term benefits for the individual. If sex primarily helps to maintain the long-term genetic well-being of species, it cannot have evolved by purely darwinian mechanisms.