Showing posts with label Biology and the natural world. Show all posts
Showing posts with label Biology and the natural world. Show all posts

Sunday, 3 September 2023

How human do you think you are?

 My essay on the Post-Human body, now freely available online at Public Philosophy Journal 'The Philosopher' thephilosopher1923.org

Monday, 12 December 2022

You sure axolotl questions


So I fell down a google hole for a little personal project I started recently on life forms that can regrow and become rejuvenated after serious injury and loss of parts. It's something I got interested in ages ago through reviewing a James Elwick book which detailed the way regeneration was a topic of fascination for biologists in the 19th Century. Apparently Richard Owen, the founder of the Natural History Museum and head honcho biology man in the UK until a certain mr Darwin came along and dethroned him, was particularly enamoured of the problem of explaining why some creatures could grow new bits to replace ones that fell off, and others could not. For Owen the ability of a lobster to regrow a claw, or a lizard to replace its tail, was a central mystery of life and held the key to understanding not only how life works but how to prolong it. 

Owen's research program fell into disfavour in the late 19th Century because he never got along very well with Darwinism. I still find his explanation for varying regenerative capacity fascinating though. He theorised that in higher life forms, the vital essence had become centralised in the nervous system, especially the brain, which is why higher forms can only reproduce if they're imbued with 'fecundating principle' A.K.A sperm. Simpler creatures have their life force spread out more evenly throughout their bodies, which is why if a fragment breaks off it can simply regrow. I don't know why this appeals to me so much.  

The axolotl is a bit of a poster child for regeneration, because it regrows not only its tail but other limbs and even internal organs.Sea cucumbers get the prize for self-repairing not just comprehensively but rapidly, regrowing lost parts in as little as a week. Hydras outdo their mythological name sake, because any fragment larger than a few hundred epithelial cells that is isolated from the body has the ability to regenerate into a smaller version of the whole. They're also thought to be truly immortal, because they show no processes of senescence -aging.  They can just renew indefinitely. A planarian flatworm can also grow back its entire body from a speck of tissue,

One interesting thing is that there is often a key area or body part that must remain intact, in order for regeneration to be viable. We all know (right?) that an earthworm's future depends on where you split it. But did you know that if you cut it after its 13th segment (counting from the head) then it can regrow its head, but not sexual organs? Whereas cutting it between segments 20 and 21 can create two whole new worms? but cut between the 23rd and 55th segments and you'll end up with no worm at all. Mind you, this is just 'red wrigglers', while 'blackworms' will actually self-amputate in response to temperature shifts. And one unfortunate species can be induced to develop a head at both ends.

Why can't humans regrow limbs and organs? The standard modern line would, I think, be that such regenerative powers in a complex multicellular would be too risky, because it would make cancers more dangerous. But this isn't really a complete explanation. Axolotls are pretty complex after all - why doesn't cancer destroy them? Why do some very complex organisms suffer little or no cancer at all? Variable regenerative power could be a product of inherited constraints, frozen into certain lineages by chance. 

Makes me wonder if there is any cool scifi imagining humans with axolotl-like abilities. Some superheroes have it, sure, but what if everyone did - how would that change society? It wouold affect our attitude towards risk, presumably. And create interesting new possibilities for body modification.

Right i should really get back to work now.............

Wednesday, 15 September 2021

Day 2 Group selection for Maynard Smith and Sober


 

So yesterday went really well. To my surprise, i did everything i'd planned!  My brain was working, i made some good headway on the talk.

Today - meh. I often find that a good, smart day is followed by a dip. And i didn't even get drunk! I just woke up and couldn't face going back to the notes i'd finished the evening before. It's not the end of the world because i was in and out of EPSA talks and meetings today anyway. 

But then this book arrived in the post and has saved me. It's a book that's kind of hard to get hold of. At least, libraries rarely have it,  and pdfs don't seem to circulate online, so i had to stump up and buy it. Which is another reason why scholars without much cash - say early career folk who pay for a lot of childcare - are disadvantaged in academia. But i don't have eye-watering childcare costs anymore, so worldofbooks got my money.

It was so worth it! For a random edited collection from 1987, its pretty widely-cited, and now i can see why.  Chapter 5 'How to Model Evolution' by John Maynard Smith, and the ensuing back and forth he has with Elliott Sober, is gold.

I think i can build one of my chapters around it (not the one i was meant to be working on, but hey)  so i'm going to put my initial thoughts about it down here.

Wednesday, 14 November 2018

Alex Byrne responds

Alex Byrne has kindly sent me a response to my post on his article, which I here reproduce in full, with his permission and his original emphasis preserved.

* * * 

"Ellen, thanks very much for this thoughtful engagement with my article. Here are some comments/replies. I’ve put the relevant pieces of your post in quotation marks.

“I'll assume Byrne recognises that the idea of defining sex by genitalia as birth, with chromosome testing as a back-up, is problematic, because he doesn't consider it. One problem is you might get people who have ambiguous genitalia and whose chromosomes are ambiguous as well - such as if they have XXY or XO chromosomes. Another problem is that people's genitalia can mismatch with their chromosomes.”

I agree completely with this. Being female or male cannot be equated with having a certain kind of genitalia, or having certain chromosomes. That is obvious if you widen the focus beyond humans. Of course, genitalia at birth are generally a very reliable sign of a (human) baby’s sex, but a sign or indication of X should not be confused with X itself. 

“Byrne argues instead that we can turn to a standard biological definition of sex to show us that sex is binary.  He suggests we use the standard biological, multi-species sex distinction which says that the female of the species is the one that produces the largest gametes. Then we can say that "females are the ones who have advanced some distance down the developmental pathway that results in the production of large gametes - ie ovarian differentiation has occurred, at least to some extent." A male, meanwhile, is someone who has advanced some distance down the developmental pathway that results in the production of small gametes - sperm.

Byrne argues that if we use this definition then there will be no humans who are neither female nor male, thus proving that sex is, after all, binary.”

But I do not say that. Here’s what I wrote:

The existence of some unclear cases shows that it would be incautious to announce that sex (in humans) is binary. By the same token, it is equally incautious to announce that it isn’t — let alone that this is an established biological fact. And even if some people are outside the binary, they are a miniscule fraction of the population, nothing like the frequently cited 1–2 percent figure, which draws on Fausto-Sterling’s earlier work.

“There are several problems with Byrne's argument.

First of all, the definition  wouldn't be easy to apply - we would have to come up with some rules about exactly which developmental events constitute the right amount of ovarian differentiation, for one thing.”

You’re right that it wouldn’t be easy to apply. But I never suggested that we adopt it as a way of telling whether a baby is female or male. Observing the genitals is a cheap and effective way of telling (although, as you point out, it won’t work for every case). I was simply interested in whether sex is binary, rather than in finding some especially reliable test for someone’s sex.

“And Byrne would have to accept that any fetus younger than 6 weeks has no sex at all, which flies in the face of normal intuitions about sex.”

Quite right. I do accept it. But surely you don’t think that biological questions should be decided by “normal intuitions”! Since I think I existed at one week after conception, I think there was a time when I was sexless. Here’s some support: “Sex is never determined at conception” (Beukeboom and Perrin, The Evolution of Sex Determination, OUP 2014, p. 17).

“Second, Byrne allows that there will still be humans who count as both male and female, because they have advanced some way towards production of both types of gamete (such individuals have standardly been called 'true hermaphrodites' but the Intersex Society of North America is campaigning for such genital-focused terms to be avoided). This, he says, is in line with the fact that definitions in biology are never perfectly precise, but always admit of exceptions. I agree, but I fail to see why his desired conclusion - that sex is binary - is not threatened by such exceptions just as it would be threatened by cases which are neither male nor female?”

You’re right that if there are humans who are both female and male, then this would refute the binary thesis. But I never allowed that there are such people. I wrote:

…there are some other rare cases (arguably 1 in 50,000 births or even rarer) that are hard to decide, but there are no clear and uncontroversial examples of humans who are neither female nor male. (A similar point goes for supposed examples of humans who are both female and male, although here things get more complicated.)


Here things really do get complicated! It would have taken much too much space to treat the (exceedingly rare) cases of so-called “true hermaphrodites”, so I had to leave that out.


“And there are women who likewise fail Byrne's definition of a female…Such individuals [XY people with (Complete) Androgen Insensitivity Syndrome] don't constitute difficult cases for Byrne's definition - they are classified unproblematically as male. But Byrne's definition would pose a problem for these individuals - at least some of them get hurt by being classified as male. Patino was hurt because she lost her career as an Olympic hurdler. Some are hurt because they feel like females. Some are hurt because they feel like neither males nor females.”

I am certainly not suggesting that everyone who is male should be socially treated as male, or barred from female-only sports, or called ‘male’, or have ‘male’ on their birth certificate, or anything like that. Cases of CAIS prove that that would be ridiculous. 

“We don't have to define sex as binary any more than we have to define indigo as separate from violet.”

Here I think we have a serious disagreement. (Well, maybe not — tell me what you think.) By my lights, I am not defining sex as binary. I am, rather, reporting that sex is basically a matter of gamete size (as I might report that water contains hydrogen and oxygen), and that people who say that sex isn’t binary (in humans) are going far beyond the evidence. 

Suppose sex is binary. We can’t change that, any more than we can change the fact that we are mammals. (Or that indigo and violet are different colors; indigo may be a kind of blue, but whatever it is it isn’t violet.) What we can change (if we like) are our practices of classifying people as female or male. We could even agree to drop that social classification altogether — remove it from government documents, tear down bathroom signs, mandate unisex clothing, and so on. I simply wasn’t concerned (in that article) with these issues. 

Consider this analogy. Let us say that northerners are those born in the northern hemisphere, and southerners are those born in the southern hemisphere. That is a binary distinction (assume no one is born exactly on the equator): every human is either a northerner or a southerner, and no one is both. Suppose that these are socially significant categories. The northerners oppress the southerners, and the different groups are supposed to wear differently colored hats. Some people feel trapped by the “hemispheric binary”, perhaps not “identifying” as a northerner or a southerner, and refuse to wear a hat at all (or maybe wear a multi-colored one). No doubt something should be done about this unhappy state of affairs. But denying that the northerner/southerner distinction is binary is not it.

best

Alex"

Friday, 9 November 2018

On whether sex is binary

Anne Fausto-Sterling is a developmental biologist who has spent decades exploring the biological and social factors that work together to produce maleness and femaleness.

Monday, 17 September 2018

Duck willies

I was having a conversation with someone the other day about how at All Souls College they sing a bizarre song about a mythical duck,

Thursday, 23 November 2017

Autumn days


We are enjoying yet another stunning autumn day here in the North of England - it’s cold but crisp, the light has a wonderful slightly honeyed clarity and the pavements are decorated with delicate origami shapes in an array of purple, yellow and dazzling red. For November 23rd this is highly irregular and I'd personally call it the best autumn in memory. The Forestry Commission predicted as much, back in August, when an unusually wet summer gave trees the opportunity to store plenty of sugars in their leaves. The following months have been almost uniformly dry, warm and still - no frosts to kill off the leaves, no water to turn them into mulch and very little wind to blow them away. The results have been breath taking. Autumn has always been my favourite time of year and the kids are used to me staring at the sky a lot and constantly stuffing fine specimens into my pockets to be pressed and displayed at home, but this year I've been insufferable. By rights it ought to be dark and damp and full-on SAD by now, but its almost December and the skylines are still dripping with  iridescent, flaming leaves.

Furthermore, I've just made a thrilling new discovery.

Thursday, 7 April 2016

Ker ching: Putting the Extended Evolutionary Synthesis to the test

Congratulations to Kevin Laland and Tobias Uller have just been awarded a stonking £5.7 million grant for an international, multi-disciplinary, project "to put the predictions of the Extended Evolutionary Synthesis to the test". It is one of the biggest awards the Templeton Foundation have ever made and it promises to be an exciting three years!

Thursday, 31 March 2016

Passing cuddles down the generations (and what else besides?)


Did you know, a mother’s love is so strong that the power of her kiss can be felt many generations after it happens? It is true of rat mother love, at least. In 2004 Michael Meaney's group published the results of a study showing that the nurturing behaviour of a mother rat brings about physical changes in her babies that are subsequently transmitted to grandchildren too. It is a fascinating example of an epigenetic effect – a change that is passed across cellular or organismal generations, even though there is no change to any DNA sequence.

Sunday, 3 January 2016

Brown and Heyes: Social learning and the other cooperation problem

This is the latest in my series of blog posts summarising the talks and responses that took place at the meeting 'Inheritance and cooperation'.

Unfortunately, some idiot forgot to press the 'rec' button on this one (an idiot called 'Clarke'). So i cannot make any audio available I'm afraid : (

Dr Rachael Brown is a Lecturer at Macquarie University in Sydney who has written about learning, its ability to act as an inheritance mechanism and its effects upon evolutionary processes. Her talk, 'Generating benefit: Social learning and the “other” cooperation problem', explored the idea of treating social learning as a cultural inheritance mechanism, and one that occurs, furthermore, in non-human animals.  

Monday, 7 September 2015

Birch and Bentley: Time and relatedness in microbes and humans

Dr Jonathan Birch from the LSE is working on a book called 'The Philosophy of Social Evolution'. For this meeting Birch drew on his recent paper 'Gene mobility and the concept of relatedness' to talk about a foundational idea in contemporary evolutionary theory - Hamilton's theory of Kin Selection - and in particular at its application in the context of what has been called 'sociomicrobiology' - the study of sociality in bacteria and other microbes.

Friday, 7 August 2015

Powers and Clarke: Insititutions and the development of human sociality

Dr Simon Powers is a member of the Lehmann group in the Department of Ecology and Evolution at the University of Lausanne, although he originally got his PhD in computer science.

Powers is concerned to explain how humans have moved from small-scale, self-sufficient tribes or kin-groups, to large-scale, differentiated exchange economies, a change which has elsewhere been called the 'Holocene transition'.

Sunday, 26 July 2015

Merlin and Clark: Extending inheritance

Dr Francesca Merlin from the IHPST (CNRS, Paris) gave a talk based on her forthcoming paper which evaluates recent calls to extend our notion of inheritance. She starts with a commonsensical notion of inheritance as 'like begets like' and claims that the notion of inheritance is intended, primarily, to explain the fact that organisms produce organisms that are similar to them. It grounds continuity across generations of living things, in other words. She argues, thus, that there is a privileged link between inheritance and reproduction.

Thursday, 23 July 2015

Helanterä and Uller: Superorganisms as model systems

For the first guest talk of the meeting, we heard from Dr Heikki Helanterä, who is a biologist from the University of Helsinki, working on eusocial insects. Heikki is beginning a new project in which he tests the idea that eusocial insect colonies can be compared with organisms. He considers the best candidates to be those colonies in which workers are sterile - terminally differentiated - because this is when 'the cool stuff happens'. For example, the queens can mate multiply, bringing all kinds of genetic diversity into the colony, because the workers aren't in a position to do anything about it.

Helanterä is interested in establishing whether sufficient heritable variation exists at the level of whole insect colonies to support a between-colony selection process, in which colonies act as units of selection in their own right.

Tuesday, 21 July 2015

Inheritance and cooperation: Clarke introducing the themes

Apparently some short girl called Clarke dreamt up the idea of linking inheritance and cooperation for the focus of a conference. An audio file of my introductory talk can be found here.  Here is (roughly) what I had to say in my defence:

Friday, 27 March 2015

Conference Announcement

Inheritance and Cooperation

June 25th & 26th, Balliol College Oxford

Heredity is understood to be a core ingredient of evolution by natural selection, and is standardly thought of as mediated by the passing of genes from parents to their offspring. Genetic inheritance underpins the theory of kin selection, which stands as a leading explanation for the evolution of cooperation. Organisms can be selected to help their relatives, because those relatives inherited some of the same genes from the common ancestor. We say that helping relatives then boosts the organism's indirect fitness. However, cooperation takes place in many scenarios in which there is no recourse to explanation in terms of indirect fitness benefits, because the participants lack a common genetic inheritance: between species; between unrelated humans; between genes; to name a few.

We are becomingly increasingly aware of the action of systems of inheritance that are not genetic. Organisms inherit, for example, epigenetic marks, niches, symbionts, culture. We are learning more and more about non-standard genetic inheritance systems such as lateral gene transfer, meiotic driver genes and transposable elements.

What happens to our ability to explain the occurrence of cooperation if we expand our conception of inheritance? Might we throw light on the possibility of cooperation between partners that fail to share a common genetic inheritance? Can other inheritance systems play an analogous explanatory role to that played by genes in kin selection theory? Are all inheritance systems equal, in this sense, or do they vary in ways that systematically affect their influence upon cooperation?

The aim of this conference is to pull together people who research different sorts of inheritance systems, or explore the impact of those systems on cooperation, to see if anything general can be extracted about the ways in which inheritance influences cooperation.

Confirmed speakers: 

Francesca Merlin (Philosophy, Paris)
Heikki Helanterä (Biology, Helsinki)
Rachael Brown (Philosophy, Macquarie)
Simon Powers (Biology, Lausanne)
Maria Kronfeldner (Philosophy, Bielefeld)
Tobias Uller (Biology, Lund/Oxford)
Jonathan Birch (Philosophy, LSE)

Wednesday, 26 November 2014

On the eco-evo-devo of cooperation


To explain the origin of any transition, it is necessary to identify some phenotypic change that brings about a new fitness benefit.

Wednesday, 17 September 2014

Kin selection and horizontal gene transfer

Microbiology / kin selection peeps, I need your help understanding something.

Here is a sentence I came across in a paper from the Sterelny/Joyce/Calcott/Fraser collection on Cooperation and its Evolution;

"According to Hamilton's rule, any modification of focal relatedness of genes specifying cooperative behaviors may have an effect on the stability of cooperative behaviors between interacting individuals." (Riboli-Sasco, Taddei and Brown 2013, 281).

I realise the many perils of basing a discussion on a single amputated sentence, but I think it is fair to represent the point being made as the following;

Friday, 11 July 2014

The price of holding a baby

Last week I learnt from Ronald Noè that female chimps (and other primates) pay new mothers (in time spent grooming) for a go on their babies. Louise Barrett and Peter Henzi actually found that the 'price' of holding a newborn monkey responds, just like that of most consumer goods in human markets, to the level of supply. Fewer babies around in the troop equals more minutes spent picking fleas out of Chimpette's fur before you get to cuddle baby Chimporino.

What I adore most about this fact is its utter irreconcilability with all our usual assumptions about why adult animals do things, in terms of fitness maximisation etc. I see nothing a monkey stands to gain from squidging someone else's little 'un (maybe I'm wrong?) except good old-fashioned cuteness.

Babies are just nice. Fact.

Friday, 27 June 2014

In praise of an unkempt garden


There are plenty of houses, in the transitional area of Oxford where I live, whose gardens are what some would call anti-social. Lawns uncut all year, rubble piled up, weeds taking over and generally making the property appear vacant, unloved and unfriendly. At least, this is the typical societal attitude towards such gardens, I think. More careful, considerate homeowners keep everything neat and tidy, which makes the whole street feel safer, keeps house prices higher and generally pleases those inclined towards neighbourhood-watch stickers in their windows. Unkempt houses make a house look empty, which implies no one wants to buy it, which will depress all the prices. Or like it might be occupied by squatters, who are terribly dangerous. Or, worst of all, like students live there.