Journal ofmedical ethics, 1987, 13, 173-178 J Med Ethics: first published as 10.1136/jme.13.4.173 on 1 December 1987. Downloaded from Fertilisation and moral status: a scientific perspective Karen Dawson Monash University, Australia Author's abstract begins with a spermatozoon, the male gamete, The debate about the moral status ofthe embryo hasgained penetrating the ovum or female gamete and culminates new impetus because of the advances in reproductive in the mingling of the genetic material from each to technology that have made early human embryo form a single-celled zygote. experimentation a possibility, and because of the public Historically, fertilisation was believed to be possible concern that this arouses. Severalphilosophical arguments only in the uterine or fallopian tubes of the female, claiming that fertilisation is the event that accords moral but recent medical advances resulting in many births status to the embryo were initiallyformulated in the context world-wide, have demonstrated that in vitro of the abortion debate. Were they formulated with fertilisation is also possible (3). Regardless of the sufficientprecision to accountforthe scientificfacts as we location of the process, its biological consequences are now understand them? Or do these arguments need the same: fertilisation restores the diploid chromosome three moralstatus number, enhances genetic variation, results in sex modification?Aspects of argumentsfor copyright. beingacquired atfertilisation are examined in relation to determination and is a necessary prerequisite for current scientific knowledge, highlighting the reasons why embryogenesis to proceed (4). such arguments, atpresent, seem toprovide an inadequate basis for the determination of moral status. Fertilisation and moral status: the arguments examined Advances in reproductive technology have made it technically possible for the early human embryo to be Arguments in support of fertilisation as the time at an experimental subject. This has enlivened debate which full moral status is acquired either rely solely http://jme.bmj.com/ concerning the moral status of the prenate (1), for on features of the fertilisation process, or on some of some consensus on this issue is essential for policy its aspects in combination with an emphasis on the formation aimed at regulating the future of such potential ofthe newly-formed entity. Those arguments research. depending on potential have been considered Within the context of the abortion debate, various elsewhere (5), so the focus here is only on those landmarks in prenatal development are nominated as arguments that rely on features of the fertilisation the determinant of full moral status. Developmentally process. For the purposes of discussing the relevant the earliest of these is fertilisation (2). This paper biology, these arguments can be considered as three on September 26, 2021 by guest. Protected examines some of the arguments for claiming that major types: the genetic argument, the discontinuity/ fertilisation is the basis for full moral status in the continuity argument and the individuality argument. context of current scientific knowledge. Have these arguments been stated with sufficient precision to cope The genetic argument with the facts as we now understand them? Do they need to be modified and if so, howtnight this be done? But before these questions can be considered some In essence, this approach pin-points fertilisation as the understanding of fertilisation itself is time at which moral status is acquired as it is then necessary. that entities that 'are genetically human beings' (6) What is fertilisation? are created. For this argument the crucial event during fertilisation is the formation of a human genotype. It Human fertilisation is a complex process requiring is claimed that only at fertilisation, and not before, about 24 hours for completion. Viewed simply, it does a new genetic member ofthe species Homo sapiens come about, and at no other point in development is Key words there any 'significant' (7) genetic change. This claim is often coupled with the basic moral principle that it Fertilisation; early human embryo; multiple births; moral is wrong to destroy innocent human beings which, if status; zygote; individual; genetics; numerical continuity. taken to include the zygote, leads to the conclusion 174 Fertilisation and moral status: a scientific perspective J Med Ethics: first published as 10.1136/jme.13.4.173 on 1 December 1987. Downloaded from that it is wrong to destroy early human life from the are needed. moment of fertilisation (8). Variation at the level of the gene is inherent in the Biologically, this view raises two major questions - genetic argument and is extremely common in nature. firstly, what constitutes the state of being genetically The simplest example of this 'natural variation' is the human and secondly, what is meant by a significant occurrence of genetic 'polymorphisms', that is the genetic change? presence in a population ofalternative forms ofa gene, Taking the first question: the genome or genetic known as alleles. This is found, for example, for the make-up of an organism may be considered at three major human blood-typing system, the ABO-blood levels - the comparatively gross level of the group, where various combinations of the alleles of chromosome, the level of the gene itself and the even this gene occur with varying incidences in different finer level ofthe molecular structure ofthe gene. Ifthe populations (16). condition of being genetically human is considered A similar degree ofvariation has also become evident chromosomally, it is either implicit or explicit (9) in at the even finer level ofgene structure since molecular this argument that one prerequisite is the presence of genetics provided an extensive array oftechniques that 46 chromosomes (23 of which are contributed by the permit fragments of the genetic material, DNA, to be egg and 23 by the sperm). Presumably these isolated and their chemical composition identified. Use chromosomes are of an accepted karyotypic of these techniques, especially restriction enzyme configuration for the number of 46 is not unique to mapping (17), has demonstrated that not all humans (10). However, a definition of being phenotypically equivalent alleles exhibit the same genetically human based on chromosome number chemical composition in different individuals. creates problems - for what then is the status of those This variation at the genetic level either in the allele who fail to fulfil this requirement? present or its chemical composition complicates the There are numerous human conditions compatible definition of an entity as genetically a human being. with postnatal life identifiable by the presence of 45, Where should the boundaries of natural variation be 47 or more chromosomes. The most extreme example drawn? Can defining a human being solely in genetic results from dispermy: two rather than one sperm terms take account of this range of variation? This enter the egg and participate in fertilisation. The result type of definition is likely to become increasingly copyright. may be the formation of a tripoid zygote (a zygote complex as more of the human genome is examined, containing 69 or three sets ofchromosomes as opposed for at present the genetic content of at most 10 per to the usual 46 or two sets). Triploidy is estimated to cent of it is known (18). occur in 1-3 per cent of all human fertilisations (11) Adoption of the claim of Noonan (19) that: '...if and in vitro as many as 8-10 per cent of fertilisations you are conceived by human parents you are human' can be observed to result from the penetration of more may be seen as a possible means of circumventing the than one sperm (12). The majority of triploids are difficulties in defining a genetic human being. In the spontaneously aborted or still-born but there are some light of recent advances in in vitro fertilisation (IVF) http://jme.bmj.com/ reports of live-born individuals who have lived for up this approach raises the question: If you are conceived to seven months after birth (13). by IVF-procedures, from human material, do you still More common conditions showing a variation in qualify as human? An affirmative answer here surely chromosome number and accompanied by much suggests that the origin of the material rather than any longer life-spans include Triple-X females (about 1/ of its characteristics is what is important for specifying 1500 live female births), Klinefelter's Syndrome a human being. However, even this possible solution (about 1/500 live male births) and Down's Syndrome may be short-lived, for it relies on species breeding (about 1/500 live births) which are usually associated true to their kind. But consider the situation of on September 26, 2021 by guest. Protected with 47 chromosomes in the karyotype. In contrast to transgenic animals. this range of disorders, postnatal existence with only A transgenic animal is one carrying a gene from 45 chromosomes is more limited. Turner's Syndrome another species, such as a mouse with a gene from a is the only such chromosomal condition in humans in human source (20). How many human genes can be which one chromosome may be completely absent. introduced into a phenotypic mouse before it is The affected females (about 1/4500 live female births) considered as genetically non-mouse or even human? are missing an X-chromosome from the genome (14). Is it the intra-uterine existence of the entity within a The incidence of