Pikmin evolved from a type of small semi-carnivorous plant that could uproot itself and move to different locations. These plants had very short life cycles, and although they fed off of small insects by secreting a sap like glue around them to ensnare them, they primarily fed on the decaying bodies of animals. Due to this, their bodies evolved to be similar to animal flesh in taste, texture, smell, and appearance.
They looked very much like a hodgepodge of plants mixed to form a creature. An upside-down radish served as the body, with small roots jutting out of random places on it. Small, tunicated onion bulbs were heads. The scape base at the top of the head grew long and thin, with more root structures growing from it. The arms were long and spindly, like thin tomato vines, and they had leaf like structures as appendages.
These creatures were a dark shade of black, usually living in large clusters in the shade of larger plants, where it was damp. Their bodies were basically two pods, one on the other, with a mass of simple root systems jutting out from numerous locations on them. These early pikmin, or Podmin, had no facial characteristics or real details, as their only life functions were breathing (in carbon dioxide, out oxygen), feeding on nutrients from animal carcasses and loose soil, and mating, by expelling small burst of pollen from their leaves. These creatures did move on occasion, but only to escape direct sunlight or to move to new soil when theirs was depleted of nutrients or began to settle. When they did move, it was extremely slow and only about a foot or two in distance.
Eventually, the vast forest the Podmin lived in began to die out. Evolution had to act fast to save the incredible roving flora. Their bodies to began to change in appearance and structure, inside and out. The first major change was within their main body and limbs. Instead of just simple, tubes pumping sugars and other bodily fluids around the organism, they evolved arteries and veins, pumping their cranberry colored bodily fluids faster through their bodies and giving them more energy to be able to move longer distances. They also grew thin yet firm wood like structures inside of them.
It was a basic skeletal structure within, basically a thin stick down the back of the Podmin, that branched off when near limbs. The limbs also had very weak cartilage-esque joints. The veins on their heads grew into a large singular leaf, and the leaves on their hands turned into more veins. These veins could be used to hold or move objects, like dirt or pebbles. With the new inner workings of the creatures, they began to move more often, moving further out of the forest, though still taking shade under larger plants.
The Podmin still faced a very hard to conquer problem: they often did not know where they were going. The weak sensory glands in the upper portion of their bodies no longer sufficed, but thanks to their semi-animal characteristics, they evolved large, black compound eyes. There were still small root endings coming from their lower torso's and upper "thigh" that helped them absorb nutrients from the ground. As the Podmin's forest became more and more savannah, the creatures were forced into open sunlight more often. As a result, their bodies changed in color from black, to grey to light grey. At this point, they were no longer Podmin, but Primin (Primitive Pikmin). This evolutionary process took about 70 years for the Podmin species to be considered true Primin.