No Saxon invasion?

[authun]

Many theories (even in physics!) do not explain the observed data in "unequivocal terms".

You'll have to pardon me for being somewhat rusty. It's been nearly 40 years since my undergraduate days but as far as I recall, if the observed data does not fit the theory, then the theory is in need of revision. In physics, observation is normally confirmation of the prediction of the theory. Regarding the Big Bang, it was my understanding that Penzias and Wilson's observation of Dicke's predicted cosmic background radiation was proof of the big bang theory. As Hoyle asked of Hawking, "Where is your fossil?" Penzias and Wilson found it and they won a Nobel prize for it.

It it as proven as it can be, given our state of knowledge.

Or rather, it confirms a current theory. Subsequent observations may require the theory to be revised.

"Final" is a red herring here. Halsall did not write about final/definitive proofs, but about "can 'prove'".

OK, I'll drop the word 'final' but where in the Weale study does Mike Weale assert that genetics "can ‘prove’ that there was mass migration and dramatic population change in lowland Britain in the fifth and sixth centuries." as Halsall claims?

I only see Weale stating; "We accept that our data do not prove conclusively that an Anglo-Saxon mass migration event took place. If a background migration rate of 0.3% is allowed between Central England and Friesland, then the need for a mass migration event disappears."

If I have missed it and if Halsall has correctly quoted Weale, please tell me where I should be looking.

Yes, they do. It's either no migration (island model, TS = infinite) or one big migration (TS = 240 generations for 6000 years BP, or 60 generations for 1500 years BP). This dichotomy is just wishful thinking and Halsall is correct to point it out.
Just read their paper:

I have, many times. Hence I am familiar with its contents and not subject to being misled by isolated extracts. As I stated from the outset, people don't read these things, at least not fully. They tend to scan them for any snippet which appears to offer confirmation of whatever view they hold. If you think it is either no migration or one big migration why do you suppose Weale explains so carefully the constraints of several population modelling algorithms resulting in his statement "We therefore developed an alternative inference method that allowed us to explore more flexible
models under a range of historical scenarios involving both background and mass migration in the presence of population splitting and growth."

If the paper was not challenged on technical grounds, then the question of expertise is moot.

If the expertise was moot, the study would not be cited in as many peer science publications as it is. And you can be sure that it would have been challenged in the peer literature if it contained errors, if conclusions were drawn from unreasonable assumptions or if reasonable assumptions were omitted.

Perhaps a Goth had an Alan father and a Thracian mother. He might even have presented himself in different circumstances as Goth, Alan or Roman. So would his DNA be 'Gothic', 'Alanic' or 'Roman'?

How he presents himself in different circumstances does not change his chromosomes. They were fixed at the time of conception. To answer your question directly, His yDNA would be the same as his Alanic father. His mitochondrial DNA would be the same as his Thracian mother. The other 45/46ths of his nuclear DNA would be comprised of that passed on from both his Alanic father and Thracian mother which in turn would include input from their respective ancestors.

Weale's study only looks at the paternal lineages of the incomers, the yDNA. It did not investigate where the anglo saxon women came from nor did it investigate, via the autosmal DNA, who these men mixed with. For that you'll have to wait for the results of the People's of the British Isles project.

As Halsall noted, they'll just drag us back 150 years ago, when Goths and Saxons were seen as biologically homogenous populations.

I don't see where Halsall says that but contrary to that statement, genetics is more likely to show an increasing complexity of settlement patterns rather than reduce them to 19th century sterotypes.

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authun