Celts used lye to artificially lighten their hair

Yes they did, and this also indicates that they were not very light-haired. Britons would have been even less.

But if C bleached their hair and B did not, that may accout for Strabos observation

Strabo wrote much later than the time when the Celts were first encountered in the 'wild'. He mentions nothing about hair bleaching in the passage in question.

"Celts used lye to artificially lighten their hair""Yes they did (...)"

Interesting! Could you please provide the source for this information?

BTW, Celtic speaking tribes were so widespread in space (East-west, from the Scots to the Galatians in Anatolia; North- South from the Gauls to the Celtiberians), it is no wonder they were so different. The Indo-European scenario ( a small population transmitting its language and culture) was no different in kind to the latter romanisation of the now Romance speaking peoples of Europe by the Romans.
Scholars refer to this process as a secondary focus of Indo-European culture.
You don´t need large numbers to bring about a language-shift.

It comes from Diodorus's history, less than a century removed from Strabo's writing.

"Their aspect is terrifying...They are very tall in stature, with rippling muscles under clear white skin. Their hair is blond, but not naturally so: they bleach it, to this day, artificially, washing it in lime and combing it back from their foreheads. They look like wood-demons, their hair thick and shaggy like a horse's mane."

>> It comes from Diodorus's history, less than a century removed from Strabo's writing.

Fashions can change rapidly. Does Strabo mention the hair-bleaching practice of the Celts? In any case, the conclusion that the Ancient Britons were darker-haired than the Celts is fairly certain, since Strabo explicitly states it, while he does not state that the Celts are more light-haired because of the particular custom.

>> You don´t need large numbers to bring about a language-shift.

History supplies us with countless examples when minorities were converted into the idiom of the conquered population. That is the case with the Visigoths, Lombards, Bolgars, Normans, etc. The Romans managed to convert linguistically the Celts because of the prestige of Roman civilization, the presence of the Roman Army and the continued influence from the center of Romanity itself, Rome, that was in contact with the provinces. These conditions do not apply to the hypothetical Indo-Europeans.

I disagree. It is highly possible that the continental Celts were still bleaching their hair within a human lifetime of Diodorus (we're talking about tribal customs, not MTV-age fashions,, and Diodorus's "to this day" implies continuity). So unless Strabo took a poll to figure out the true rate of natural blondism in Celtic tribes, then all bets are off.

There is no "to this day" in the original Greek. It's fairly well-known that the aboriginal Britons were mainly dark-haired. Even today in those regions of the British Isles least affected by Continental invasions, the population is mainly dark-haired. There is no reason to doubt that Strabo could not distinguish real blond hair with artificially lightened hair, especially since the method of lightening it changed its texture and appearance as well.

(1.) *OI( DE\ *GALA/TAI TOI=S ME\N SW/MASI/N EI)SIN EU)MH/KEIS,
TAI=S DE\ SARCI\ KA/QUGROI KAI\ LEUKOI/, TAI=S DE\ KO/MAIS
OU) MO/NON E)K FU/SEWS CANQOI/, A)LLA\ KAI\ DIA\ TH=S KATA-
SKEUH=S E)PITHDEU/OUSIN AU)/CEIN TH\N FUSIKH\N TH=S XRO/AS
(2.) I)DIO/THTA. TITA/NOU GA\R A)POPLU/MATI SMW=NTES TA\S
TRI/XAS SUNEXW=S [KAI\] A)PO\ TW=N METW/PWN E)PI\ TH\N @1
KORUFH\N KAI\ TOU\S TE/NONTAS A)NASPW=SIN, W(/STE TH\N
PRO/SOYIN AU)TW=N FAI/NESQAI *SATU/ROIS KAI\ *PA=SIN
E)OIKUI=AN: PAXU/NONTAI GA\R AI( TRI/XES A)PO\ TH=S KATER- (5)
GASI/AS, W(/STE MHDE\N TH=S TW=N I(/PPWN XAI/THS DIAFE/-
(3.) REIN.

>> You don´t need large numbers to bring about a language-shift.

"History supplies us with countless examples when minorities were converted into the idiom of the conquered population. That is the case with the Visigoths, Lombards, Bolgars, Normans, etc. The Romans managed to convert linguistically the Celts because of the prestige of Roman civilization, the presence of the Roman Army and the continued influence from the center of Romanity itself, Rome, that was in contact with the provinces. These conditions do not apply to the hypothetical Indo-Europeans"

Linguistic "conversion" of a majority by a minority can happen without the props of an empire. It can happen without a centralized power. In fact, Mr. Pontikos, the hypothesis for Indo-European spread you seem to favor (that of C. Renfrew) does without it. According to Renfrew, Indo-European languages followed the wave of Neolitic agriculturals from Anatolia.
While the time-table does not fit with known linguistics facts (i.e., it seems unlikely the earliest recorded I.E. languages would not have further departed in form if we posit so many millenia of separation), diffusion accounts for many cases of successful language groups spoken by scant numbers of speakers displacing "majority" languages.

>> Linguistic "conversion" of a majority by a minority can happen without the props of an empire. It can happen without a centralized power. In fact, Mr. Pontikos, the hypothesis for Indo-European spread you seem to favor (that of C. Renfrew) does without it. According to Renfrew, Indo-European languages followed the wave of Neolitic agriculturals from Anatolia.

No, I don't think in particular favor Renfrew's theory; you must be aware that Renfrew's theory is one of demic diffusion rather than elite dominance. Demic diffusion can only work if there is a significant demic component, i.e., if many people move into an area, then they will take their language with them, just as the Slavs took their language in the medieval period. On the other hand, there has been no such demic diffusion in post-Neolithic times in Europe that would explain the distribution of Indo-European languages.

"On the other hand, there has been no such demic diffusion in post-Neolithic times in Europe that would explain the distribution of Indo-European languages."

What is your hypothesis? Wherever they originated -and that´s a moot point-, there is still no convincing explanation for the replacement of indigenous pre- Indo-European languages. It is also interesting to bear in mind that earlier Indo-European languages (as documented by ancient hydronyms, "Altereuropäisch") were also drowned in the sea of Germanic, Slavic and Celtic languages, while genetically, by all accounts, Europeans have changed little since neolithic times.
Please correct me if I am wrong ;-)

I'm doing an assignment on the Celts, and i was wondering if anyone knows anything on Strabo, and his perspective on the celts, if you do, can you please email me asap?

What is your definition of a "Celt"? According to Gerhard Herm (1975), there was some confusion on the part of the Romans regarding the distinction between some Celtic and Teutonic "tribes".
Herm defines the ancient Celtic people as a cultural and linguistic group, rather than as a "racial" group united by certain physical traits.
Certainly, those who self-identify as Celts today and the present inhabitants of "Celtic" nations are not the same people Strabo and other Roman writers identified as Celts. (but I digress).
It is also possible that not all of the many ancient northern tribes referred to by Roman writers and identified by modern theorists as "Celts" maintained identical cultural practices. The separation between Gaelic speaking peoples of the British Isles and mainland Celts in particular would probably have led to divergent cultural practices. The influence of "invading" Teutonic peoples on continental Celtic tribes would have contributed to this divergence (and may also have led to confusion on the part of Roman writers) And then there is the question of the influence of pre-Celtic peoples, possibly of Mediterranean origin, upon the Celts who settled in what we know today as Great Britain.
In terms of linguistics, of course,today Celtic languages are spoken only in limited areas of Great Britain and Ireland. I even read somewhere recently that some linguists define Scots as "one of the two Germanic languages spoken" on the Islands. Well, I think that's crap. But then I would, wouldn't I? :-)
(The Celts: The People Who Came Out of the Darkness Gerhard Herm, 1975) IMHO, anyone interested in the Celts and pre-Roman times in northern Europe would enjoy this book.