New research findings from a study of 634 couples found that the more often they smoked marijuana, the less likely they were to engage in domestic violence.
The study, conducted by researchers in the University at Buffalo School of Public Health and Health Professions and Research Institute on Addictions (RIA), appeared in the online edition of Psychology of Addictive Behaviors in August.
The study attempted to clarify inconsistent findings about domestic violence among pot-smoking couples that primarily has been based on cross-sectional data (i.e., data from one point in time). Looking at couples over the first nine years of marriage, the study found:
• More frequent marijuana use by husbands and wives (two-to-three times per month or more often) predicted less frequent intimate partner violence (IPV) perpetration by husbands.
• Husbands' marijuana use also predicted less frequent IPV perpetration by wives.
• Couples in which both spouses used marijuana frequently reported the least frequent IPV perpetration.
• The relationship between marijuana use and reduced partner violence was most evident among women who did not have histories of prior antisocial behavior.
The study's lead author is Philip H. Smith, PhD, a recent doctoral graduate of the UB School of Public Health and Health Professions and now associate research scientist in the Department of Psychiatry at Yale University.
It is based on research data collected by lead investigator Kenneth Leonard, PhD, director of the UB Research Institute on Addictions. The study was supported by a grant from the National Institute on Alcohol Abuse and Alcoholism to Leonard and a grant to Smith from the National Institute on Drug Abuse.
"These findings suggest that marijuana use is predictive of lower levels of aggression towards one's partner in the following year." Leonard says. "As in other survey studies of marijuana and partner violence, our study examines patterns of marijuana use and the occurrence of violence within a year period. It does not examine whether using marijuana on a given day reduces the likelihood of violence at that time.
"It is possible, for example, that -- similar to a drinking partnership -- couples who use marijuana together may share similar values and social circles, and it is this similarity that is responsible for reducing the likelihood of conflict.
"Although this study supports the perspective that marijuana does not increase, and may decrease, aggressive conflict," he says, "we would like to see research replicating these findings, and research examining day-to-day marijuana and alcohol use and the likelihood to IPV on the same day before drawing stronger conclusions."
Of course, there was hanky panky between the two groups long before modern humans showed up in Europe. So here's the scoop:
Neanderthals and modern humans were both living in Europe for between 2,600 and 5,400 years, according to a new paper published in the journal, Nature. For the first time, scientists have constructed a robust timeline showing when the last Neanderthals died out.
Significantly, the research paper says there is strong evidence to suggest that Neanderthals disappeared at different times across Europe rather than being rapidly replaced by modern humans.
A team, led by Professor Thomas Higham of the University of Oxford, obtained new radiocarbon dates for around 200 samples of bone, charcoal and shell from 40 key European archaeological sites. The sites, ranging from Russia in the east to Spain in the west, were either linked with the Neanderthal tool-making industry, known as Mousterian, or were 'transitional' sites containing stone tools associated with either early modern humans or Neanderthals.
The chronology was pieced together during a six-year research project by building mathematical models that combine the new radiocarbon dates with established archaeological stratigraphic evidence. The results showed that both groups overlapped for a significant period, giving 'ample time' for interaction and interbreeding. The paper adds, however, it is not clear where interbreeding may have happened in Eurasia or whether it occurred once or several times.
Professor Thomas Higham said: 'Other recent studies of Neanderthal and modern human genetic make-up suggest that both groups interbred outside Africa, with 1.5%-2.1% or more of the DNA of modern non-African human populations originating from Neanderthals. We believe we now have the first robust timeline that sheds new light on some of the key questions around the possible interactions between Neanderthals and modern humans. The chronology also pinpoints the timing of the Neanderthals' disappearance, and suggests they may have survived in dwindling populations in pockets of Europe before they became extinct.'
In 2011, another Nature paper featuring Dr Katerina Douka of the Oxford team obtained some very early dates (around 45,000 years old) for the so-called 'transitional' Uluzzian stone-tool industry of Italy and identified teeth remains in the site of the Grotta del Cavallo, Apulia, as those of anatomically modern humans. Under the new timeline published today, the Mousterian industry (attributed to Neanderthals and found across vast areas of Europe and Eurasia) is shown to have ended between 41,030 to 39,260 years ago. This suggests strongly that there was an extensive overlapping period between Neanderthals and modern humans of several thousand years. The scientific team has for the first time specified exactly how long this overlap lasted, with 95% probability.
The Uluzzian also contains objects, such as shell beads, that scholars widely believe signify symbolic or advanced behaviour in early human groups. One or two of the Châtelperronian sites of France and northern Spain (currently, although controversially, associated with Neanderthals) contain some similar items. This supports the theory first advanced several years ago that the arrival of early modern humans in Europe may have stimulated the Neanderthals into copying aspects of their symbolic behaviour in the millennia before they disappeared. The paper also presents an alternative theory: that the similar start dates of the two industries could mean that Châtelperronian sites are associated with modern humans and not Neanderthals after all.
There is currently no evidence to show that Neanderthals and early modern humans lived closely together, regardless of whether the Neanderthals were responsible for the Châtelperronian culture, the paper says. Rather than modern humans rapidly replacing Neanderthals, there seems to have been a more complex picture 'characterised by a biological and cultural mosaic that lasted for several thousand years'. The Châtelperronian industry follows the Mousterian in archaeological layers at all sites where both occur. Importantly, however, the Châtelperronian industry appears to have started significantly before the end of Mousterian at some sites in Europe. This suggests that if Neanderthals were responsible for both cultures, there may have been some regional variation in their tool-making, says the paper.
Professor Higham said: 'Previous radiocarbon dates have often underestimated the age of samples from sites associated with Neanderthals because the organic matter was contaminated with modern particles. We used ultrafiltration methods, which purify the extracted collagen from bone, to avoid the risk of modern contamination. This means we can say with more confidence that we have finally resolved the timing of the disappearance of our close cousins, the Neanderthals. Of course the Neanderthals are not completely extinct because some of their genes are in most of us today.'
Previous research had suggested that the Iberian Peninsula (modern-day Spain and Portugal) and the site of Gorham's Cave, Gibraltar, might have been the final places in Europe where Neanderthals survived. Despite extensive dating work, the research team could not confirm the previous dates. The paper suggests that poor preservation techniques for the dating material could have led to contamination and false 'younger' dates previously.