The idea that "humans use technology to extend themselves" is somehow a sub culture "movement" that distinguishes itself by "using technology to extend humanity", is false. Technology is and was what made us human, back with Homo habilis. Nothing has changed in that sense. Humans are "trans primate", already, since 2.5 million years and then increasingly so. To frame the defining characteristic of the human species as a "sub culture" is just a form of elitism, deictically, and, complete nonsense.
The dominant root belief of the cult of "transhumanists" is the neuron-transistor analogy. It is false, and one simple way to see that is the sheer size of neurons. Neurons are roughly 0.01 mm in diameter. That's the size of transistors in the 1970s. Today, computers have transistors that are roughly 1000x smaller. The idea that biology would use what humans were using 50 years ago, is clearly false.
Tubulin are 4.5 x 8 nano meter, a nano-scale transistor. Smaller than what is used in modern computers, but, close. They are the transistor of the cell including neurons, the cell itself comparable to an integrated circuit with billions of molecular switches. 
Obviously, if neurons are transistors, then the total computation humans have created would begin to approach the capacity of the human brain. Neurons are not transistors. "transhumanism" is just a cult. The memes that are loudest in ordering genes to replicate them have a survival advantage, "immortality" has always been a popular myth, today, and thousands of years ago. Nothing has changed. "Transhumanism" is just good old double-speak, reversing the meaning of words.
interesting have heard about it but got to know a lot today in details :)