-1 SECTION 4:
REPRODUCTION
This section has been omitted from the original text, revised and expanded upon, due to so much interest in theories involving Irken reproduction. It now stands as its own section.
When discussing the theories surrounding Irken reproduction, it is important to bear in mind that which I have stated previously, which is that Irkens are more akin to insects than any other known life form. Inasmuch, one can deduce that the reproductive organs and mating behaviour of an Irken can likewise be compared to an insect. Now, I have received some criticism to this point. Many out there argue that Irkens cannot be insects. I did not say to a degree of certainty that Irkens were insects, but that they share many similarities with insects, and probably evolved from an insectoid creature. And I also made clear that I classify them in the same order as insects due to the facts that they share so many anatomical features with insects, and that this is the only taxonomic unit relevant enough to group them into. Someone asked me why Irkens have a spine if they are an insect.
Simply, a spine is an evolutionary feature designed to house a more complex spinal cord. If Irkens evolved from insects, they would have needed to evolve a spinal cord, which is better suited for carrying higher amounts of information than a traditional nerve clusters throughout the body found in many invertebrates. Irkens have a brain and a complex nervous system, meaning that they need a large spinal cord, meaning that they need a spine. Now, before we get too nerve-ous…on to reproduction.
From merely watching the show, one can see that there are two distinct sexes of Irken, male and female. Just like humans, male Irkens have a lower voice than their female counterparts, which indicate that Irkens have hormones comparable to estrogen and testosterone, respectively. Female Irkens have a more pronounced curl to their antennae than males, and the eyes of a female Irken are more angular, whereas a male's are more rounded, but this has been stated before. I just wish to settle the debate once and for all that there ARE differences between male and female Irkens.
I have recently been queried about an interesting biological feature that I probably would have otherwise overlooked. That being the lack of breasts on female Irkens. We as a mammalian race take certain features of our own bodies for granted. Mammals are some of the most highly evolved, complex life forms to ever exist. Comparing the mammalian body to that of say a fish would be like comparing a carbureted engine to the latest computer controlled fuel injected sports car engine. To answer this question, we must turn back to my classification of Irkens as (at least a type of) insects. Insects do not nurse their young as mammals do, ergo, they do not have mammary glands. (I beg maturity from the readers at the following): Mammary glands are the structures found near and attached to the nipples of female mammals that produce milk used to feed the organism's young until they are capable of feeding themselves. This feature is found only in mammals, as mammalian young take longer to reach a developmental stage where they become self-reliant than the young of any other classification of organism. Whereas this feature has resulted in a closer bonding between parent and offspring, and the formation of societies among mammals, it is not found among any other life form known to modern science.
As seen in "Parent Teacher Night", Zim was hatched, and then promptly ordered to duty. Upon hatching, he could stand, talk, and exhibited full motor function and awareness of his surroundings. This indicates that Irkens are capable of taking care of themselves from birth, and don't need the presence of a parent Irken to nurture them until maturity. This type of offspring independence is quite commonplace in the insect and arachnid world. There are certain species of spiders whom, once hatched, immediately set upon devouring their mother. Most insects take no part in the lives of their offspring, and once their eggs are laid, they leave to mate again or to die, depending on their specie.
So it's safe to say that if Irken young are capable of taking care of themselves from birth, Irken females do not need mammary glands. If they don't need mammary glands, they don't need larger breasts in which to house them. Question answered. Next!
Another question which resulted in me taking the time to rework this entire section was (here it comes) "How do Irkens reproduce?" I've heard a recent theory that they are hermaphroditic, and can reproduce asexually, and one very intelligent reader suggested that Irkens are diploid, or have two sets of chromosomes, which would explain the shortage of female Irkens. As well thought out as this question is, I'm afraid I have to argue with you, my friend. Many species on Earth are capable of asexual reproduction. In fact, it is a mainstay among the lesser life forms to simply split and reproduce the chromosomes, form two new complete cells, break off, and call it a day. This simply doesn't occur in higher life forms, as the processes needed to carry out such a division would be too complicated. You're no longer talking about replicating a nucleus, a mitochondria and cell walls, but complete tissues and organs.
Some species of flatworms, once divided in half, can form two new identical flatworms. I'm not going to get into this one, but it is believed by me that Irkens, because of their complexity and clearly defined sexuality, do not reproduce in any manner besides that in which all other higher life forms reproduce: sexual reproduction.
Because there are male and female Irkens, I can deduce that each carries half of the chromosomes needed to form a new Irken. By the combining of these chromosome-containing sex cells, one female and one male (I'll leave how THAT may happen to those who enjoy ZATR fics), a new Irken smeet…or rather the zygote that will become a new Irken smeet…is formed.
On the show, it appears that Irkens no longer use mating to produce children. Rather, Irken children, or smeets, are "hatched" from large containers, which probably serve the purpose of artificial wombs. In a nutshell, Irken scientists (no doubt in an attempt to supply large numbers of Irkens for the empire's vast military needs), artificially combine male and female sex cells, probably from screened individuals with desired traits, and allow the smeets to grow in these tubes. Such "smeet farming" procedures would ensure a constant supply of Irkens, and be more productive to such a race than mating.
However, despite these breakthroughs in artificial population control, it can be assumed that Irkens still possess the ability to mate, and even if banned by law, such mating and reproduction probably still does occur among Irkens.