genes - Science-Education-Research

Can ancestors be illegitimate?

Does discriminatory language suggest biologists are ashamed of some of their ancestors?

Keith S. Taber

Historically, some offspring have been classed as illegitmate and so unable to claim the same rights as those recognised as legitimate children.

But are biologists treating some of our ancestors as illegitimate?

This is a bit like judges in a court of appeal announcing their decision as "the appeal is successful – the criminal is innocent".

I was listening to an old podcast recently. The first item was about how nearly all Inuits have a particular genetic variation that is adaptive to living in the Arctic with the extreme cold and restricted diet that involves. These particular genes are not unique to that group, but are only found with much lower incidence in other groups living elsewhere. These genes are in the human 'gene pool', but have been strongly selected for among Inuit communities where they are now ubiquitous.

However, what was seen as especailly interesting about this particular genetic resource was its 'origins' – from another species. These genes are considered to have arisen in Homo sapiens by transfer from another species: Denisovans.

I do not think that any present day humans have any Denisovan or Neanderthal genes

So, the claim is that modern humans have some Denisovan genes just as (according to scientific studies) we have some Neanderthal genes, and probably genes from some other archaic human species as well. Actually I argue below this is not the case, but my argument is in terms of semantics rather than being a rejection of the substantive claims.

So – spoiler alert – I do not think that any present day humans have any Denisovan or Neanderthal genes, but I am happy to accept that we may have genes acquired from other human species such as the Denisovans and Neanderthals. To explain the distinction it is useful to ask how did 'we' modern humans come to be given this genetic gift?

Who counts as an ancestor?

What I thought was of special note in this item of the episode of BBC Inside Science was the language in which it was explained. The programme description suggested:

"Can Inuit people survive the Arctic cold thanks to deep past liaisons with another species? Adam Rutherford talks to geneticist Rasmus Nielsen who says that's part of the answer. His team's research has identified a particular section of the Inuit people's genome which looks as though it originally came from a long extinct population of humans who lived in Siberia 50,000 years ago. The genes concerned are involved in physiological processes advantageous to adapting to the cold. The conclusion is that at some point, the ancestors of Inuits interbred with members of this other species of human (known as the Denisovans) before people arrived in Greenland."
https://www.bbc.co.uk/programmes/b08558n5

The expert interviewed on the episode explained:

"…what we think we can conclude now is that in fact this D.N.A. that we find in the inuits, that we think was important for them in adapting to this extreme environment, that actually was transferred to them from Denisovans or from somebody related to the Denisovans, and by transferred, how does that work, well that works by interbreeding, so in the past we know there has been some interbreeding between these Denisovans and the ancestors of modern humans, and when they interbreed of course you transfer D.N.A."
Prof. Rasmus Nielsen, University of California at Berkely

At the end of the item, the presenter reiterated:

"So, the ancestors of Inuits bred with the Denisovans, and the gift of that blessed union, were genes that helped with cold adaptation."
Dr Adam Rutherford

Now I am not a biologist, and so am perhaps I missing a nuance of how terms tend to be used in biological discourse, but all three of these statements seem to include the same logical fault.

The 'interbreeding' events being referred to are a great many generations back in time, but to ilustrate my complaint, I have prepared a much simplified diagram modelling the scenario presented in the programme, but with just a few generations:

A simplified representation of who counts as an ancestor – according to some biological discourses

Excluding ancestors from minority groups

Now it seems the account being presented by biology here only makes sense if we distort the usual meaning of 'ancestor'. Surely a person's ancestors are all those people who feature on direct lines of descent to that person? In my simplified figure the individual at the bottom has eight great-grandparents.¹ In my understanding of 'ancestor', each of these eight people is an ancestor of the individual shown in the final generation. If that is accepted then each of the quotes above is misphrased:

at some point, the ancestors of Inuits interbred with members of this other species of human (known as the Denisovans)
in the past we know there has been some interbreeding between these Denisovans and the ancestors of modern humans
the ancestors of Inuits bred with the Denisovans

Well, no. Surely what is meant here is:

at some point, those ancestors of Inuits considered members of Homo sapiens interbred with other ancestors of Inuits who were members of this other species of human (known as the Denisovans)
in the past we know there has been some interbreeding between these Denisovans and the other ancestors of modern humans
the ancestors of Inuits considered members of Homo sapiens bred with the ancestors of Inuits considered Denisovans

The original statements are akin to telling someone that they are the result of their parent coupling with a communist (or: an Australian / a graphic designer / a Liverpool supporter / a goth / a sociologist, etc.), as if a communist (or sociologist, or whatever) does not deserve to be recognised as a genuine parent.

There seems to be discriminatory language here, a kind of speciesism, where only those ancesters we consider part of 'our' species count as proper ancestors, and so other kinds of human are illegitimate as ancestors.

Two types of sex: Normal sex…and something a little shameful?

This is reflected in implying that there is some abnormal type of sex going on between these different classes of humans. Normal sex is all about genetic recombination (that is, the advantage of sexual over asexual reproduction is the 'shuffling' of genes from two individuals to give different, and pretty much unique, genetic permutations in the offspring).²

But the 'interbreeding' between species is described in particular language – a 'transfer' of genes. Now, in some parts of the living world we do see a kind of transfer of genes where one organism 'donates' copies of some its genes to another organism.

That is somewhat different from breeding in human populations that relies on meiosis to produce gametes that each have half of the parental nuclear genes; and which co-contribute to a new version of the human genone when fertilisation occurs due to the fusion of two gametes – nothing is actually transferred. Like downloading a file from a website where there is not really a 'file transfer' but the copying of an orginal that remains where it was. ³

That process of sexual reproduction is what occured when two ancestors bred – regardless of whether both were Homo spaiens or one is Denisovan (or Neanderthal or some other type). So, what is meant by 'transfer' is presumably that some 'Denisovan genes' were copied into the H. sapiens gene pool.

The species question

This description would make sense if species were ontologically discrete entities. But, as Darwin (1959) long ago realised, there are not sharp, absolute distinctions between species, and biological demacractions of species are more matters of 'convenience'. If we have some 'Denisovan D.N.A.' or 'Neanderthal D.N.A.' in our genomes, then – assuming the Denisovans or Neanderthals did not have genetic engineering skills long before 'us' – then the Denisovans or Neanderthals are our ancestors.

And why not? The very logic of evolution is that if we go back far enough in time we have:

non H. Sapiens, indeed, eventually,
non-human,
non-primate, even
non-mammalian, ancestors.

Humans today may be different from Denisovans or Neanderthals, but then we are also surely somewhat different to early sapiens who had not yet got friendly enough with Denisovans or Neanderthals to have received 'transferred' genes.

So, is the language here, of transferring genetic matieral by interbreeding (contrasted with the genetic recombination occuring when speciments of H. sapiens bred), reflecting a traditonal view of species that Darwin invalidated?

That is, under the old definition, members of two different species cannot breed to provide offspring, or at least, not fertile offspring. But the Denisovans and Neanderthals that 'interbred' with our (other) ancestors and passed copies of their genes indirectly down to humans today, clearly had no trouble in that department. Nor can it be argued that these were geographically separated populations that never overlapped, and so can be considered consequently as if separate species. Clearly there must have been some degree of co-habitation between these groups to allow matings to occur.

There may be significant enough objective differences between the morphology of early Sapiens, Denisovans and Neanderthals for biologists to feel these should be considered different species, but the notion that Denisovans and Neanderthals can simply be considered as being distinct entities on other discrete branches of the evolutionary bush is challenged by the evidence that at least some of themare among our direct ancestors. Perhaps only a minority of the Denisovans and Neanderthals that shared the world with Homo sapiens have offspring alive today – but then that would likely also be true for their sapien peers.

The science teacher and philsopher Gaston Bachelard has described how science is often impeded by retaining the 'fossilised' infuence of historical ideas that science has supposedly moved on from. Is this an example? The BBC Inside Science podcast seems to be telling us we need to rethink what we mean by our ancestors, whilst using that very word without taking this into account. This is a bit like the judges in a court of appeal announcing their decision as "the appeal is successful – the criminal is innocent".

No more discriminatory language

Or, is this an example of using language loosely to communicate effectively, because being precise would lead to convoluted expressions [like my 'at some point, the ancestors of Inuits considered members of Homo sapiens interbred with other ancestors of Inuits who were members of this other species of human (known as the Denisovans)']?

Modern humans do not actually have Denisovan or Neanderthal genes, or Denisovan or Neanderthal D.N.A., but rather have some genes that are identical (or very similar) to – in effect indirect copies of – some genes of their Denisovan or Neanderthal ancestors. And no doubt those genes (or rather identical genes ⁴) could also be found in some of their even more distant ancestors who are in turn considered a different species again. After all, humans share many genes with many other living things, such as bananas, so references to 'human genes' or 'Denisovan genes' it is a bit like referring to characters in the Roman alphabet as 'English letters', when they are equally 'French letters' or 'Dutch letters', etcetera. They are letters that appear in English language texts, but they are not exclusive to English language texts: just as there are genes found in human genones that are not exclusive to human genones.

Referring to 'Denisovan genes' or 'Denisovan D.N.A.' speeds communication. But it has potential to mislead the non-specialist.

So, I object to any of my forebearers who happen not to be considered specimens of Homo sapiens being said to 'transfer' genes when they 'interbred' with my ancestors: they are just as much my ancestors as those partners they engaged in genetic recombination with.

So, please, no more more discriminatory language directed against some of our ancestors, just because they were in minority human groups.

Work cited:

Bachelard, G. (1938/2002). The formation of the scientific mind. A contribution to a psychoanalysis of objective knowledge (M. McAllester Jones, Trans.). Clinamen Press.
Darwin, C. (1859/2006). The Origin of Species.

Note:

¹ In a genuine family 'tree' there are likely to be mulitple offspring from some unions, and indeed often some people will parent children with multiple partners – but this would over-complicate the diagram as it is not central to the argument being made.

In a case such as this with just four generations we would expect a person to normally have eight different great grandparents who are all unambigously three generations distant from that individual. As we consider much longer time periods it becomes increasing likely that the same ancestor occupies several (indeed, many) 'slots' on the tree (you have many fewer than 2ⁿdistinct ancestors going back n generations once n gets large) and indeed these individuals may appear in the tree across several generations.

If you are not convinced by that, please see 'Intergenerational couplings in the family: A thought experiment about ancestry'

Another way of thinking about this is that not all of your (great)ⁿ grandparents will have been alive at the same time, once n starts is more than a small number. As an extreme case, it is quite possible that the offspring of a union between a 50 year old man and a 20 year old woman (unusual but not unknown) might quite feasibly have had one pair of grandparents who died before the other grandparents were born. This is unlikely, but plausible. With each additional generation it becomes less likely that all your ancesters at that remove were alive at the same time.

² The advantage of asexual reproduction is that the outcome should be a viable specimen in the envrionment occupied by the parent that has been cloned. Perhaps the most advanced reproducers are those species that are able to reproduce by either strategy?

³ And, just as teaching does not seek to 'transfer knowledge' from the teacher.

⁴ Perhaps one issue here is how we can use the term, gene, to refer both to functional sequences of nucleic acid in abstract (as we might refer to 'the carbon atom' when we mean all and any carbon atoms, not a specific one), and actual material samples. In the first sense, a parent and offspring can share the same gene; in the second sense, a copy of a parent's gene can be passed to the child. In neither sense does the 'transfer' of genes occur.

I could not have been born to different parents…

A reflection on free will, determinism, justice, ignorance, and identity

Keith S. Taber

This morning I listened to a really interesting podcast on 'Free will, retribution and just deserts', with Prof. Gregg D. Caruso being interviewed about his ideas by David Rutledge.

The question of free will (as opposed to a rigid determinism) is one of those matters that most people seem to instinctively feel they know the answer to: we all feel we have free will. Why did I decide to write this blog rather than do something else this evening? Clearly I think that I freely decided to do this because this was something I wanted to do. Yet, that it feels like a free choice, means little. We may also think that life would lack any meaning in the absence of free will, and that being free agents is a much more attractive proposition; but wanting something to be the case is not much of an argument for thinking it is so.

If everything is predetermined (perhaps by the initial conditions of the big bang plus the fixed laws of the universe) then those people who think they have free will must have no choice but to think so (as it was determined), just as those who (correctly, in this scenario) reject free will cannot be given credit for this insight. (Actually, I doubt anyone really believes that they do not have free will, not even any off-duty philosophers, as I am not sure how one can live one's life that way – as just an observer of the automaton that others identify with you, as a viewer of the unfolding movie that is your life?)

How much is ending up here an accident of birth rather than the outcome of deliberate 'free' choices? (Image by jraffin from Pixabay)

I found much of Caruso's argument convincing, in particular in relation to the justification of judicial incarceration. My moral instincts are that if the state takes away someone's liberty this should be because it is acting to protect society or its vulnerable members, and not as an act of retribution.

Caruso argued that we should take note of how so many people in the prison system have mental health issues or addictions, and he pointed to the strong associations between convictions and poverty or other limiting or damaging socio-economic conditions. This raises issues of social justice, and when treatment and rehabilitation are more productive responses to crime than punishment per se. Caruso was primarily using the example of the situation in the United States, where he suggested most inmates have mental health issues, but his general points apply more widely.

The lottery of life

However, there was one point at which I became uneasy with the argument, where Caruso brought in what is sometimes referred to as the "there, but for the grace of God, go I" position. If we accept that people born in poverty and squalor, or brought up in neglect or abuse, are those most likely to enter the criminal justice system as offenders, then those of us fortunate enough to have been born into relative privilege should acknowledge how lucky we were in the lottery of life, for "there, there, but for the grace of God (or, indeed, pure chance), go I".

Caruso noted:

"I could just have easily been born into low scoio-economic status, or homelessness, or born with a mental illness".
Gregg D. Caruso

Image by Michelle Maria from Pixabay
Image by Herbert Hansen from Pixabay

I know exactly what he means, and agree we should acknowledge our advantages over those less lucky than ourselves, but, strictly, I cannot accept that argument.

I think the argument can only work if one believes (a) in an immaterial soul, which is only housed in the body during mortal life, and could have just as easily journeyed through life in a different body; and (b) even if that soul may impact on the actions of that body in its environment, it is is not changed by those experiences; and (c) that this soul is the true 'I', the identity of the person who refers to themselves as I (in "I could just have easily been born into…"). Of course, some people may believe just that. But I suspect most people who do believe in some kind of dualism involving something like an eternal soul imagine it is able to (and perhaps even intended to) learn from its incarnation(s).

Who am I?

Even having the debate assumes that one accepts that it makes sense to acknowledge a discrete and relatively stable 'I' (and there are plenty of commentators who feel that this individual self identify soon starts to dissolve when examined too closely). I am happy to acknowledge a kind of distinct and not-overly-plastic 'I', as I think I know what I mean by 'I', and my experiences of that self seems stable and discrete enough to reify it. My self certainly changes, but not so radically and quickly that I awake a stranger to myself (sic) each morning.

But then this 'I' could not just have easily been born into low scoio-economic status, or homelessness, or born with a mental illness.

I was very lucky to be born in a country at peace, in an open society that had a national health service and free education for all; and to loving, caring and supportive parents who were never violent or intoxicated. Money was tight when I was a young child, and the flat where I spent my first few years might not have passed health and safety inspections by today's standards: but we never went hungry, or had to wear torn or dirty clothes; and we slept in proper beds in a secure building; and there was coal for the fire each winter's morning. (For younger readers, coal is a carbon-rich combustible rock which was delivered to homes and used as fuel in open fires in the distant past – releasing filthy dust when handled, and producing choking, polluting smoke when burnt. But, once upon a time, even the rich used it for home heating!) My father always had at least one part-time job alongside his full-time employment to make ends met, but he still always found time to spend with my sister and I when he could be at home. Yes, in the lottery of life, I was very lucky.

Could it have been different?

As I started this post talking about determinism, I should acknowledge that if everything is predetermined, then clearly it could not have been any different! Although I cannot logically refute this possibility I behave as though it has been rejected.

It would seem

a) if I do not have free will then I am only appearing to make choices about what to type (and whether to think I have free will), and even if there was any point worrying about this, whether I do worry about it or not is totally out of my control;

and

b) if I do have free will then I gain nothing by assuming, or acting, as though it is otherwise.

(That is, there is a kind of parallel to Pascal's wager going on here – if you have free will than a bet on anything other than free will looses everything; and if you do not have free will then there is no actual bet to be had, only the illusion of one, and nothing more can be lost).

So, assuming that the course of my life has been the outcome of the choices I have made, and those of my parents, and my friends, and my teachers, and everyone else who's decisions have ever had any influence on my life, then the self I identify with today has been constructed through my experiences of the world, impacted by others, and iteratively built up as I reacted to situations by developing my values and personality; which then influenced (i) my actions and interactions in the world, and so (ii) others' responses to me, and so (iii) the experiences I drew upon in developing that self further…

This is of course just a variation on the constructivist account of learning as incremental, interpretive, and iterative – as we build up our conceptual structures, our mental models of the world, our perspectives, our worldviews, our value systems, our ideologies, our beliefs, our attitudes, our habits, our metacogniti0n, our preferences, our epistemological commitments, and so forth (and these all interact of course) we build up our selves. Indeed, what is the self, if not the gestalt, or perhaps the subsuming system, of these facets of our selves?

Counterfactual 'me'?

So, if my parents had neglected or abused the child who grew to be me then that child would have become someone different to the person I am now, someone else. Even if I had not ended up incarcerated 'at her majesty's pleasure' [sic, a term which reeks of retribution rather than restoration], I very much doubt I would have ever been admitted to a University, or become a teacher, or met my wife (when she decided to do an evening class in physics), or got to teach at Cambridge…

This was Caruso's point, of course, that 'there, but for the grace of God…' – but it would not (by definition) be me who was someone else, as I (the person writing this now) would never have existed. How different that other person would have been is an open question, but I suspect substantially and significantly different.

The sins of the fathers…

But then my parents could not have neglected me or abused me. I do not mean that the people who became my parents could not, under different circumstances, have become very different people and so different kinds of parents – of course that might have been possible. But those hypothetical people are not the parents I know – they would have been quite different people.

If I had been born in another country… but then no, I could not have been.

Perhaps, under different circumstances, my parents might have emigrated before I was born (not so unlikely as relatives emigrated to Australia and New Zealand when I was young). But my parents, as they developed in their actual circumstances, were not those people, and if the people who became my parents had, under other circumstances, under different life experiences and influences, moved abroad before having children, then again, the self I am would not have developed.

The lottery of making life

Indeed, the resulting person might have been very different. After all, I am, not just the result of a social environment, but the unfolding in dialogue with that environment of a biological potential that is genetic. My particular set of genes is not only a unique combination because of the unique genotypes of each of my parents, but is one of myriad potential unique permutations of crossing those two unique genotypes – one particular outcome of the lottery of making life.

If the people who became my parents had emigrated to another country (or even moved to another town) before having children then I would almost certainly not have been born. The number of possible genotypes that could have resulted from crossing my parents (so to speak) is immense. The chances of my genotype becoming the basis of an implanted zygote, and leading to a child, is minuscule (except in the deterministic scenario when it is 1, but I have chosen to (/been predetermined to) disregard that scenario). If my mother had conceived somewhere else – it would not have been me that was conceived.

For, without wishing to be insensitive here, if conception had taken place the day before I was actually conceived, or the day after, it would (almost certainly) not have led to the same union of gametes, and the same me. Indeed, if conception had been delayed a few minutes to make a cup of tea, brush hair for longer, clean teeth… or perhaps had been brought forward by not brushing hair or teeth for as long… then if conception had still occurred (by no means assured) my genotype would almost certainly not have arisen, but would likely have remained one of the vast multitude of possible human genotypes that has never been called upon to guide (or channel, or afford) the biological development of a person.

Given that, you can probably anticipate how I might respond to the hypothetical "had I been born to different parents" – it is a meaningless question. I could not have been born to different parents. We are all very unique. We are also very lucky to be here at all.

Had, say, Henry VIII not fallen out with the Catholic Church, or had Luther's theses blown away, or if Alfred had taken more care over the cakes, I almost certainly would not have been here at all, in the sense that my genotype would likely have never have been expressed (given that it only takes a trivial change in a small domestic detail in the preceding generation to abort or trigger a specific conception, think about the knock-on effects over many generations once one conception is changed), and I certainly would not be here as the person I am today. (And if by some strange fluke of extreme improbability – anything that is not impossible could happen – a baby with 'my' genotype had been born in Victorian England, or even the same time as me but in a Welsh mining village (where they extracted those rocks we all used to burn), then despite some likely similarities, my 'twin' would not be me. After all, even actual 'identical' twins born on the same day in the same place to the same parents are not actually identical (e.g., they develop different fingerprints.)

The veil of ignorance

So the 'there, but for the grace of God, go I' argument does not really make sense to me ,as it should really be 'there, but for the Grace of God, goes someone else' – which rather lacks the same rhetorical impact.

However, I was recently listening to a different programme where Rawls's theory of justice was being discussed, and his notion of the veil of ignorance. The argument here is that people should judge what seems fair on the basis of having no knowledge of their own position in the pertinent social system.

So, perhaps at the end of a science lesson a teacher complains that the practical apparatus and materials have not been properly put away. The teacher offers the class a choice: everyone can miss the start of their break, till everything is cleaned and tided away; or, she will draw lots and select six students to do all the cleaning and tidying, and the rest can go to their break on time. As long as the class decide their preference BEFORE the teacher draws lots, they remain behind the veil of ignorance.

So, in the context of the penal system, the principle suggests that, for example, one needs to decide whether or not it is just and appropriate that someone who has been convicted for the third time of a minor drug offence should be sentenced to many years of imprisonment (at great public expense) before one knows whether one is lucky enough to be brought into the world in a loving, comfortable home, or born to a childhood of poverty and neglect.

Of course, that is, in principle, one should decide from the other side of the veil – we cannot actually regress to that state of ignorance. (Imagine that science teacher first telling the class which six students would be assigned the detention, but then asking the class to chose between the two options without taking that into account!)

In practical terms, this seems little different to Caruso's formulation, as both involve an impossible hypothesis (being born in different circumstances but being the same person; making an intellectual judgment before being born at all!)

Yet I think there is an important difference from the perspective of science education.

Asking someone to make a judgement on what is just without regard to their particular circumstances, whilst sensible in theory, is surely obviously impossible in practice: we cannot put aside knowledge that is essential to us, so it clearly can only be a kind of thought experiment where people do their best to disregard knowledge that actually frames or permeates every aspect of their thinking.

From my perspective, as outlined above, the same should be true of the "what if you had born born in poverty/to abusive parents/in a totalitarian state, etcetera." formulation as that is equally non-viable, and can only be a hypothetical argument. Yet, I am not sure sure that is so obvious to some people. There is something of a common notion that a person is their genes, or at least their genes determine them. Science suggests otherwise.

These two individuals share a lot of genes – but not all their genes! (Image by klimkin from Pixabay)

Whilst it is certainly true that with different genes 'you' will be a different person (and indeed with enough different genes… 'you' may be a carrot – that is, with different genes, there is no you, but someone/thing else), but it is certainly not true that someone with your set of genes will necessarily be the person you are. Your genotype had the potential to support the development of a vast range of different people (albeit that range is still a tiny region of the even more enormous array of possible people the general human genome could give expression to).

Unless, that is, my wager is lost and everything is determined. Then you must be you, but not just because you could not have had a different genotype, but also because that genotype could not have been expressed in a different environment, so the developing person that became you could not have had any different formative experiences either.

Sources cited:

Rutledge, D. (2021, 31 Jan). Free will, retribution and just deserts. The Philosopher's Zone.

Watts, R. (2021, 21st Jan). John Rawls's 'A Theory of Justice'. Arts & Ideas.