Intersexuality - Introduction

Biological Footnote: Plants and Animals

Before discussing human intersexuality in more detail, it may be useful to cast at least a cursory glance at “hermaphroditism” in lower animals. There are plant or animal species that possess both female and male sex organs and thereby increase their chances to reproduce. Biologists call these species “hermaphroditic”. In addition to countless hermaphroditic plants, there are many double-sexed animals, especially among the invertebrates and fish. Some can act and reproduce as either females or males, others change their sex as the situation allows or requires. This is another example of the enormous diversity of life on our planet. To give just a few examples:

• The flatworm phylum Platyhelminthes can function as either a female or male, producing eggs or inserting sperm into his counterparts.These, in turn, can also act as females or males.
• The fish Hypoplectrus can act as a male and release sperm in one instance and then, in the next instance, act as a female and release eggs.
• The black sea bass may start life as a female and then turn into a male.

From the left: 1. The flatworm phylum Platyhelminthes (natural size: ca. 4cm/1.5 inches) 2. The fish Hypoplectrus 3. The black sea bass

However, as one moves higher on the evolutionary ladder, this useful hermaphroditism becomes increasingly rare. In mammals, the existence of both female and male characteristics in the same body is an atypical, problematic development. The best example is well known to cattle breeders: The so-called freemartin is a female calf that, before birth, shared certain hormones with its male twin. These “masculinizing” hormones were enough to prevent the normal development of its female sex organs. The result is almost always sterility. However, twinning in cattle does not occur very often.
These few reminders must suffice here. The following text restricts itself to human intersexuality.