is evidence of genetic protective elements against alcohol dependence in many native americans, which has further discredited theories of its biological inevitability. spanish colonization 1769 marked the beginning of spanish military and religious missions to assimilate chumash in the alta region of california, roughly around modern-day santa barbara. this date also coincides with apparent changes to the chumash environment and way of life that invoked declines in chumash health. prior to colonization, the chumash enjoyed ecological abundance and diversity even during cyclical droughts and el niño events, indicating a millennia-long period of acclimatization to their environment. however, this stability was significantly altered by european contact. traditionally, historical narratives have attributed declines in chumash health to european oppression. however, this narrative has been replaced by a more nuanced perspective consisting of exacerbated environmental fluctuations from overpopulation and over-utilization of natural resources due to spanish colonization. this effect was in conjunction with the devastating effects of european diseases on chumash people, which likely began impacting the chumash in the late 16th century. the effect of spanish overpopulation and resource depletion is documented by catholic missionary fr. gregorio fernandez in 1803. his letter documents the increasing number of chumash migrants to spanish missions, not because of increasing conversions but because of the devastation of chumash agriculture and plants (particularly their staple of the acorn) caused primarily by overexploitation of spanish cattle-grazing. the religious conversion of chumash also corresponds to documented disease increases and poorer health post-colonization recorded by even the early spanish conquistadors. controversial practices fossil bird bones and talons in tar, found in kern county, california, similar to that encountered by chumash indians polycyclic aromatic hydrocarbon consumption polycyclic aromatic hydrocarbons (pahs), a chemical product of fossil fuels found in substances such as gasoline, tar, and cigarettes, cause adverse health effects such as neurological disorders, hormonal disruptions, and fetal abnormalities. before the industrial era, the predominant form of pahs was found in natural bitumen from fossils, and the chumash ancestral homeland was of the most concentrated regions of bitumen in the world. they utilized it in myriad materials, including the waterproofing of tomol canoes and water-carrying baskets. thus, the chumash have been a target of interest for research on pah exposure, owing to their prolific use of pah-containing bitumen over the previous millennia (with evidence of use in objects as far back as 10,000 years ago). wärmländer et al. have studied the skeletons of chumash between 6500 bce and the beginning of significant european contact (mid-1700s) and found a number of consistent decreases in chumash health over the time of bitumen use. among these markers was systematic decreases in skull size for both males and females over the studied timescale, indicating both decreased birthweight and neurological development over millennia. while such adverse health outcomes are consistent with pah exposure, some researchers dispute that there is a direct link between bitumen use and decreased chumash health over millennia. chumash expert patricia lambert of utah state university has questioned this hypothesis, citing the need for increased research on the controversial topic. cancer prevention and remedy cancer is another controversial topic among chumash researchers and medical professionals, as pah exposure increases the incidence of cancers. chumash methods were developed to deal with cancer management. spiritual practices, integral to chumash medicinal practices, sometimes included the use of hallucinogenic substances, along with techniques such as hypnosis though chanting. it is also hypothesized that a number of plants consumed by the chumash may have alleviated the harmful effects of pah exposure, leading to modern theories about botanical and nutritive cancer-prevention substances. sacred datura datura (also called momoy by the chumash) is a hallucinogenic plant commonly consumed as a liquid in traditional chumash spiritual practice. early anthropological records indicate adolescent males and females would receive datura from a "giver" when seemed ready for its rite of passage. typically, chumash restrictions on diet and sex would be observed by individuals before ingestion. the effects of datura often would consist of up to a day of incapacitation, the length of which was viewed to indicate the spiritual strength of the individual. hallucinations or dreams of animals such as hawks or coyotes were viewed as marks of a successful datura experience. the effects of datura, however, vary greatly by dosage, and current understanding indicates lasting adverse physiological effects from days or even months after ingestion. the most significant side-effect of datura can be death, as the lethal dose of the drug is slightly more than the necessary dose to produce hallucinations. deaths from datura in chumash communities were often seen as the fault of the drinker, who was assumed to have deviated from the necessary dietary or sexual restrictions, or have chosen to not come back from the experience. for this reason, the use of datura has been criticized as being too dangerous, especially as its use is often begun in adolescence.