The early spear was an extension of the tooth. With a spear, we could have the equivalent of a Saber Toothed tiger’s ability to capture animals. – but since the spear was not a part of our faces, we could evolve and innovate that weapon outside of us, cutting out millions of years of development time to grow the equivalent of that object organically and internally. Externalizing objects and proesthetics rapidly sped up our ability to evolve. If the spear is a technology that extends the capability of the tooth, the hammer was an extension of the fist.
Prostheses have externalized our evolution by allowing us to create technologies outside our bodies. Externalizing functionality allows defective pieces to be thrown away, as well as but we've internalized the best parts over time -- in evolution.
Later on, humans externalized transportation. The wheel, the horse, the train and carriage. The development of written symbols to represent communication served to The industrial revolution brought us the vehicle, and the Internet brought us the browser.
A hammer, whose general shape has not changed much over the past thousand years, is perfectly suited to a series of specific tasks - namely hammering. It's a verb now. The object itself represents its action, and the verb form of the object represents the action as well. You can have attach adjectives, such as "shiny hammer" or heavy hammer.
But nothing about the early computer suggests what it may look like in its future manifestation. Nothing about the telegram wire informs the onlooker that it’s eventual form might be an iPhone. Nothing about a massive computer in a gymnasium, full of cathode ray tubes and punch cards, suggests that in 60 years, it might fit in the palm of the hand.