The Great Pheromone Myth

6. The Elusive Snarks Case Studies of Nonhuman Mammalian “Priming” Pheromones

SIX The Elusive Snarks Case Studies of Nonhuman Mammalian “Priming” Pheromones To seek it with thimbles, to seek it with care; To pursue it with forks and hope; To threaten its life with a railway-share; To charm it with smiles and soap! For the Snark’s a peculiar creature, that won’t Be caught in a commonplace way. Do all that you know, and try all that you don’t: Not a chance must be wasted to-day! For England expects—I forbear to proceed: ’Tis a maxim tremendous, but trite: And you’d best be unpacking the things that you need To rig yourselves out for the fight. From the Fourth Fit, “The Hunting,” in Lewis Carroll’s The Hunting of the Snark The influences of urine or body odors on the endocrine state of mammals of the same species have been attributed to “priming” pheromones. Although most claims of such pheromones have been made for rodents, some have been made for non-rodents, including dogs, sheep, goats, and humans. The possibility that humans have priming pheromones has captured the imagination of scientists and laypersons alike, and is among the topics addressed in Chapter 7. There are few claims for the chemical identification of most so-called 98 NONHUMAN MAMMALIAN “PRIMING” PHEROMONES 99 priming pheromones and, as in the case of putative releasing pheromones described in Chapter 5, the isolated agents appear to fall short of mimicking the parent stimuli. Moreover, few have stood the test of replication. Although one cannot deny the influences of bodily secretions and excretions on the reproductive physiology of a range of animals, the question is whether such influences can be reasonably and uniquely ascribed to pheromones. To what degree is experience involved? Are the stimuli too complex or idiosyncratic to be identified? To what degree do the stimuli represent abnormal chemical stressors? Can subsets of multi-chemical mixtures induce equivalent responses? All of these questions fall to the heart of the issue as to whether pheromones are involved. The Ram Sexual Pheromone In many breeds of domestic sheep, seasonally anestrous ewes isolated from rams for a period of time exhibit, following the presentation of a ram, a rapid rise in luteinizing hormone (LH) levels and a preovulatory LH surge resulting in ovulation 35 to 40 hours later. This effect has been attributed to a pheromone since ovulation can be induced by the presentation of a ram’s fleece or extracts of a ram’s wool (Knight and Lynch, 1980) and since physical and visual contact are unnecessary to produce this effect (Watson and Radford, 1960). Cohen-Tannoudji et al. (1994) sought to chemically isolate the “ram sexual pheromone.” Sexually experienced multiparous ewes served as subjects. Various stimuli were initially assessed for their ability to produce the LH response in the anestrous ewes: (1) male urine, (2) an extract from whole fleece from a sexually experienced ram, (3) an extract from wool collected from either the head or shoulder of such a ram, (4) an extract collected from the flanks and hindquarters of a sexually experienced ram, (5) an extract from female wool, and (6) secretions from the orbital glands below the ram’s eyes. Significant LH pulses were induced by (2), (3), and (4), but not by (1), (5), or (6). From these findings, these authors concluded that the active agent is “produced and/or spread over the whole body of the male” (p. 960). However, no specific chemical fraction could be isolated that produced the effect. These investigators candidly noted the following: 100 THE GREAT PHEROMONE MY TH The male-female chemical communication involved in primer pheromone action or “male effect” appears to involve a complex olfactory pattern, rather than an accurate balance of a few specific compounds. Thus, the transmission of the characteristics of the male of the species results from a cognitive procedure, and not from a codified message conveyed by some kind of “labeled line.” The male’s chemical signature could result from a complex mixture of the variety of secretions from the multiple androgen sensitive glands. In such a perspective, the identification of some of the critical compounds is an important step, but does not allow a complete understanding of the message. (p. 960) It is important to point out that a number of sensory stimuli other than odors can similarly produce this effect. Thus...