Friday, 7 May 2010

Some Pieces of Another Puzzle

First, please have a look at this picture gallery.

Readers may have wondered why I included the last picture - apart from the obvious physical resemblance. As I said in another post:
My hair's darker, but has red highlights like hers. And my hair's longer. My brow isn't ridged. But otherwise, we could be sisters - or at least relatives.

There is mitochondrial evidence showing little (if any) genetic mixing between H.Sapiens and H.Neanderthalis. But I can't help wondering. There is other evidence that says there may have been interbreeding. Apart from people like me.
Looks like I was right to wonder.



From the National Geographic:
According to a new DNA study, most humans have a little Neanderthal in them—at least 1 to 4 percent of a person's genetic makeup.

The study uncovered the first solid genetic evidence that "modern" humans—or Homo sapiens—interbred with their Neanderthal neighbors, who mysteriously died out about 30,000 years ago.

What's more, the Neanderthal-modern human mating apparently took place in the Middle East, shortly after modern humans had left Africa, not in Europe—as has long been suspected.

"We can now say that, in all probability, there was gene flow from Neanderthals to modern humans," lead study author Ed Green of the University of California, Santa Cruz, said in a prepared statement.

That's no surprise to anthropologist Erik Trinkhaus, whose skeleton-based claims of Neanderthal-modern human interbreeding—previously contradicted with DNA evidence—appear to have been vindicated by the new gene study, to be published tomorrow in the journal Science.

"They've finally seen the light ... because it's been obvious to many us that this happened," said Trinkaus, of Washington University in St. Louis, Missouri, who wasn't part of the new study.

Trinkhaus adds that most living humans probably have much more Neanderthal DNA than the new study suggests.

"One to 4 percent is truly a minimum," Trinkaus added. "But is it 10 percent? Twenty percent? I have no idea."
Some more than others, I imagine.
The genetic study team reached their conclusion after comparing the genomes of five living humans—from China, France, Papua New Guinea, southern Africa, and western Africa—against the available "rough draft" of the Neanderthal genome.

The results showed that Neanderthal DNA is 99.7 percent identical to modern human DNA, versus, for example, 98.8 percent for modern humans and chimps, according to the study.
In addition, all modern ethnic groups, other than Africans, carry traces of Neanderthal DNA in their genomes, the study says—which at first puzzled the scientists.
...
So how did modern humans with Neanderthal DNA end up in Asia and Melanesia?

Neanderthals, the study team says, probably mixed with early Homo sapiens just after they'd left Africa but before Homo sapiens split into different ethnic groups and scattered around the globe.

The first opportunity for interbreeding probably occurred about 60,000 years ago in Middle Eastern regions adjacent to Africa, where archaeological evidence shows the two species overlapped for a time, the team says.
And from another NatGeo article:
But a new study of Neanderthal skeletons suggests the species grew quickly but reached sexual maturity later than so-called modern humans—and quite possibly survived to a ripe old age.
Again, some of us more than others - though 47 years old is taking the concept of "late development" a bit far. Something went awry in the mix.

The actual paper on the subject is A Draft Sequence of the Neandertal Genome by Greene et al.

Now for a cognitive lateral arabesque: a segue, if you like. From The Neanderthal Theory:
This theory approaches the problem from a new radical viewpoint. Instead of approaching autism as a disorder, brain defect or the result of poor socialization or parenting, it claims that autistics are fully functional.

All the areas that are central to autism are related to species-typical adaptations that vary widely between species. These include nonverbal signals, social organization, sensory acuteness, motor skills, general preferences, sexuality, physical traits and biological adaptations. Some of this diversity in autistics is poorly understood and virtually unresearched and therefore is not published in peer-reviewed journals. Because of this lack of research, Aspie-quiz, an online questionnary, is heavily referenced for these traits.

Recent genetic research have demonstrated that the Out-of-Africa (OoA) model with no interbreeding fails to explain nuclear DNA diversity in Eurasia. Several models of interbreeding that do explain this diversity exists today. It therefore is quite likely that Neanderthals contributed to the Caucasian genome. Aspie-quiz have demonstrated in a large survey in the US population that Afroamericans have only 1/6 of the autism prevalence of Caucasians. The same survey also indicates that Asians and American Indians have about 1/2 of the autism prevalence of Caucasians.
Which correlates rather well with the proportion of Neanderthal DNA in those populations - there being considerable genetic intermixing between AfroAmericans and Caucasians in the USA.

Again, from a previous post of mine:
These are all parts of a puzzle. You see, despite Autism as being seen as a "male disease", it also aflicts a greater than expected number of TS women. That is, people who are genetically and somatically male, but neurally at least partially female. There's even a special Yahoo Support Group because so many people have both Autism or Aspergers, and Transsexuality.
There is known to be a statistically significant correlation between Asperger's Syndrome and Gender Dysphoria but the nature and implications of the link are unknown. Having both of these conditions is quite a plateful and gives us special challenges.
To put it mildly.

Interestingly enough, when my metabolism went hormonally berserk, I lost the minor symptoms I had of a mild case of Asperger's, indicating that the problem may be at least partially hormonal, as well as connected with congenital neuroanatomy. We just don't know, like so much else to do with the brain, gender, and hormonal influences.
And from yet another post of mine:
Gosh I love this! It's a detective story, where we're being given clues. Moving right along... now comes the juicy bits
Altogether, females had the largest gray matter volumes in all but two significant clusters, which were located in the left and right putamen. Here, MTF transsexuals had the largest gray matter volumes
More "typically feminine" than the usual factory model... or should we say that most women are less "typically female" than TS women? Less "strongly gendered" on average? You'd expect TS women to be more "strongly gendered" than average, as many would otherwise be able to cope with transsexuality without seeking treatment. But what about the rest of the brain? Many TS women show more typically male abilities in instinctive ballistics calculations for example.
For the remaining clusters, MTF transsexuals had the smallest gray matter volumes, but their data spectrum largely overlapped with that of males.
Fascinating! Not just more female than female in some areas, but slightly more male than male in others! I wonder, is this environmental? Would the same thing be shown in younger, "primary" transwomen? Or could it be that the anomalous hormonal wash in the womb bollixes things up in an even more complex manner than we thought? We're in the realm of conjecture here, so we can't say without a lot more study. One thing - there's a correlation between Transexuality and what has been described as "ultra male syndrome" - Asperger's. Might this "ultra-male" grey matter pattern be the cause? And could a change to a female hormone regime cause changes to it?
I'm not yet ready to formulate a coherent conjecture. We have pieces of a puzzle that give tantalising glimpses of a whole, but that's all.

Rate of Transsexuality does not appear to correlate with any ethnic group - and that's important because it means Trannsexuality and Neanderthal DNA proportion are not connected.

But I am wondering if we can have the same effects regarding ASD - Autism Spectrum Disorders - from multiple causes, all resulting in neuroanatomy that is anomalous in specific areas. Could the hormonal whoopsie that causes transsexuality via anomalous neural development in many areas also cause some of the same effects as having rather more Neanderthal in one's ancestry than most - which also causes similar anomalies in just one or two areas?

Gosh, if only we knew more about Neanderthal endocrinology, it might explain so much.

OK, I know, "Neanderthal Endocrinology" is about as abstruse a subject as you can get, not exactly a popular research topic of interest to the masses, but I'm interested!

I have no complaints about the neurological effects of having Neanderthal DNA in my genes. But did I also have to get the ribcage too? And the shoulders? And the nose? *SIGH*

7 comments:

Anonymous said...

Fascinating.

Closely related species can have very different endocrinology, hyenas providing an extreme example.

It's conceivable that different (sub)species of genus Homo had different hormone levels, e.g. that the average Neanderthal womon had higher testosterone levels than the average Sapiens Sapiens womon.

In that case, Neanderthal brain development would need to protect female core sex identity from higher testosterone levels than Sap Sap brain development would. The rates of XY female transsexualism and XX male transsexualism would be roughly equal within each population, but XY female transsexualism would be more common in hybrid children of Sap Sap mothers, and XX male transsexualism would be more common in hybrid children of Neanderthal mothers.

That said, this draws on the assumptions that (1) Neanderthal womyn had higher testosterone levels than Sap Sap womyn and (2) that prenatal hormone levels trigger the differentiation of core sex identity.

Marja Erwin

Anonymous T-Girl said...

This subject fascinates my boyfriend and i. But i've never thought of how it might relate to transsexuality before.

On a side note, i still have not been able to find *any* medical study *anywhere* looking for participants.

If you ever hear of one that's open, i would appreciate a head's up.

stassa said...

Actually, your ribcage and nose etc are perfectly Cro-Magnon. Your anatomy is that of a typical male modern human. However, your neurocircuitry is not- it's more Neanderthal-typical, therefore it recognises your typical-for-a-modern-male anatomy as that of a typical-for-a-Neanderthal-female one. You see, compared to the robust Neanderthals, gracile modern human males look positively female.

In other words, when your Neanderthal brain looks at your modern body, it sees a Neanderthal female- and therefore it expects your body to be and function as female.

Oh, hi btw :)

-dr Thookov

Bex (Vicky/Alex) said...

wow.... you just managed to pull about half of my abstruse interests and put them into one place, and correlate them. i'm impressed! when I was in college studying genomics a few years back, we were learning about the team that was trying to reconstruct the Neanderthal DNA to do this experiment. Until I read your entry here, I had not heard the results.

I'm a trigendered (and fluid gendered) individual blogging my way through working out being tri/fluid gendered. Thanks for all the detail in your entries! Its amazing. Feel free to check out my blog.

www.neverburnbridges.blogspot.com

Zoe Brain said...

Hi Dr T!

According to my Endo, my ribcage is 3 Standard Deviations from the male norm (38" under the arms, 45" under my boobs), as is my wingspan, which greatly exceeds my height.

That could be just down to an anomalous puberty. Measurements of my spine are consistent with someone about 6ft, but I'm 5ft 6". My legs are too short for the rest of my body, basically.

I've seen the same phenomenon in other women, when the bone ends close off earlier than usual.

There's other anomalies too. Mild Pectus Carinatum for one.

If you look at the gallery, you'll see a similar pattern of anomalies in the CAH case illustrated. This may be systemic, or it may be coincidence, I've seen no data on the subject.

I'm going off 2nd hand opinions here, "what my endo told me", my lack of knowledge is obvious.

Thanks for dropping round - please have a traipse through the archives. I think you might enjoy it.

Eli said...

Hi Zoe!

You wrote about the yet secret but apparently existent connection between autism and transsexuality.

Do you know this two pages?

http://www.ncbi.nlm.nih.gov/pubmed/20094764

http://leftbrainrightbrain.co.uk/2009/06/autism-and-gender-identity/

adepta said...

Intriguing theory, Zoe.

I'm still preparing to discuss my own findings on the matter, but I figured I would give my list of sources here, so that others reading this can investigate if they feel like doing so:

Anecdotal reports of a link between transsexuality and interest in math, science, engineering and the like:

- Lawrence, Anne and Bailey, J. Michael. Transsexual groups in Veale et al. (2008) are "Autogynephilic" and "Even More Autogynephilic". Archives of Sexual Behavior, 38: 173-175 (2009) (Includes a bunch of additional citations for further reading. It's by the J. Michael Bailey group, which is evil in a great many ways, but even a broken clock is right twice a day.)
- "My Gender Workbook How to Become a Real Man, a Real Woman, the Real You, or Something Else Entirely", by Kate Bornstein, pg. 102.
- http://www.codinghorror.com/blog/files/Next-Generation-Online-Game-Designers-Just-Wanna-Be-Girls.htm
- http://www.transsexual.org/aprimer.html

Previous analyses with statistically significant samples:
- http://www.hrawareness.org/tgacad.pdf (on trans astronomers)
- http://grok-code.com/37/famous-programmers-from-adleman-to-zimmermann/ (on trans programmers)

On transsexuality and autism-like characteristics:
- de Vries, Annelou; Noens, Ilse; Cohen-Kettenis, Peggy; Berckelaer-Onnes, Ina, and Doreleijers, Theo. Autism Spectrum Disorders in Gender Dysphoric Children and Adolescents. Journal of Autism and Developmental Disorders, 22 Jan. 2010. (This is the journal write up of the conference talk linked by Eli; it includes a bunch of citations for further reading and is quite recommended.)
- http://itsnotmyfault.wordpress.com/2008/06/16/transgender-vs-asperger/

On transsexual IQ:
- Smith, Yolanda L.S.; van Goozen, Stephanie H.M.; Kuiper, A.J.; Cohen-Kettenis, Peggy T. Transsexual subtypes: Clinical and theoretical significance. Psychiatry Research, Volume 137, Issue 3, 15 December 2005, pgs. 151-160. (important quote: "The homosexual group's mean IQ score (111.2; SD = 16.9; n = 82) was lower (P < 0.001) than that of the nonhomosexual group (mean = 122.3, S.D. = 17.3, n = 61). There were no differences in IQ scores between the sexes (81 MFs, 62 FMs). Mean scores for the different transsexual subgroups were 107.3 (S.D. = 14.3) for the MF homosexuals (n = 39), 121.7 (S.D. = 17.2) for the MF nonhomosexuals (n = 42), 114.8 (S.D. = 18.4) for the FM homosexuals (n = 43), and 123.7 (S.D. = 17.8) for the FM nonhomosexuals (n = 19)."; I quite frankly have not the foggiest idea what would account for this)