A recent study based on one infant tooth suggests Neanderthals breastfed their babies exclusively until 7 months, and fully weaned them at about 14 months. (http://www.nature.com/news/infant-tooth-reveals-neanderthal-breastfeeding-habits-1.13047)
"The proportion of barium recorded in tooth enamel shot up immediately after birth, because breast milk contains high levels of the element. Ratios waned as mothers began to supplement the infants’ diet with other food, and then dropped to low levels when breastfeeding ceased."
However, barium amounts in teeth do vary by environmental exposure. A study by Miller* reported that the ratio of barium to calcium in the teeth of 34 children exposed in one community to drinking water containing high concentrations of barium (10 mg/L) was five times higher than that for 35 children from another community exposed to lower levels (0.2 mg/L). So comparing a Neanderthal tooth to a modern-day tooth assumes that we have had similar levels of environmental exposure to barium.
Nevertheless, Go Neanderthal moms! I'm assuming you had no breastfeeding pain relief - or pain relief of any kind for that matter.
* Miller, R.G., Featherstone, J.D.B., Curzon, M.E.J., Mills, T.S. and Shields, C.P. Barium in teeth as indicator of body burden. In: Advances in modern environmental toxicology. Vol. IX. Princeton Publishing Co., Princeton, NJ. p. 211 (1985).