You can tell a lot about a person by their phone. "Where they goin’, where they been," as Forrest Gump said. Actually, he may have been talking about shoes, but what he said does still ring true for our mobile devices: You can tell a lot about the people of a given generation by looking at their mobile phones.

On April 3, this technology -- on which most people rely in their work and personal lives -- turned 40 years old, and evolves more rapidly each day. From the first cellphone call in 1973 through the iPhone, we look at the mobile phone's history -- and what it might look like 10 years from now.

Mobile Phone Beginnings

The first working mobile phone was used by Motorola inventor Martin Cooper to call his professional rival, Joel Engel, head of research at Bell Labs in 1973. The phone Cooper used weighed 2.5 pounds, was the size of a 10-inch brick, and had 20 minutes of battery life -- more than enough time for Cooper to tell Engel that he was second-rate.

But mobile phones didn’t gain FCC approval and enter the commercial market for another 10 years. And back in the 1970s, people were much different than they are today -- most didn’t even have answering machines in their homes. And with ATMs still scarce, digital technology wasn’t even a thought for most. If you called someone on the phone and he or she didn’t pick up, that was pretty much the end of it. For better or worse, connecting with another person in the 1970s meant meeting someone in an actual physical place (far out, right?).

 In June of 2009, Mark-Paul Gosselaar made an appearance on Late Night with Jimmy Fallon with the DynaTAC 8000x -- the first commercially available mobile phone, which he used as Zach Morris on the sitcom Saved By The Bell. Image via Mavromatic.com

The first mobile phone sold commercially in 1983 -- the DynaTAC 8000x -- cost $3,995 ($8,700 today, if adjusted for inflation), had just 30 minutes of battery life and still looked like a giant brick with a big rubber antenna. It took another few years before mobile phone technology caught on, and for the most part, people still connected much like they did in the 1970s.

Incidentally the term “the Internet” was also coined in the early 1980s. During this time, both young technologies continued to sprout in parallel until the two were combined sometime in the 1990s.

Mobile Phones in the '90s

In 1992, the Nokia 1011 offered the first platform for the international GSM standard, and the first PDA and phone combo device -- in the form of the Bellsouth/IBM Simon Personal Communicator -- was introduced in 1993.

Though new mobile phones with different styles were released regularly in the early '90s, the technology was still young and awkward enough that people still used pagers. A September 1994 article in The Chicago Tribune boasted that pagers would soon allow users to leave voice messages for one another. “The effect will be like having a wireless answering machine on your belt or in your purse,” said an executive from a now-extinct company called PageNet.

The Nokia 9000 Communicator was released in 1996 and could be considered the first smartphone. It had a display that looked similar to what’s found on a graphing calculator, but it could do email, fax, telnet, Web browsing and SMS texting. It even had a whopping 8 MB internal memory and an Intel 386 processor. Remember 1996? First Tom Cruise was a spy and then he was looking for love. Help me help you. You had me at hello. Those were simpler times.

Speaking of late-'90s movies, in 1997, Val Kilmer used this technological marvel in The Saint. And it's around that time that mobile phone technology really started to take off. The iconic Nokia 3210, released in 1999, became one of the most popular phones ever, with more than 150 million devices sold. The following year, the Nokia 3310 was released and went on to sell more than 125 million units.

Toddlers are strangely comfortable with smart devices, as demonstrated by 21-month-old Elle Saarinen, who is pictured playing a game on her mother's iPhone. AP Photo/ Thomas Whisenand

Mobile Phones in the New Millennium

Between 2000 and 2012, the number of mobile phone subscriptions grew from approximately 750 million to 6 billion worldwide (there are about 7 billion people, to put that into perspective). So in 40 years, the cell phone went from non-existence to a device that is owned and used by virtually everyone.

When the original iPhone was released in June 2007, it raised the standard for mobile devices. Touchscreen technology was not as precise or easy to use as it is today, and many consumers still weren’t convinced that touchscreen keyboards were a good idea.

But the sleek design of the new Apple device raised expectations, and it drove the mobile market for years, leading to the development of many of the slim, highly-functional devices that people use today. Even Blackberry finally gave in this past January, releasing a smartphone without a physical keyboard, a device that one could easily mistake for any number of competing iPhone clones.

As technology converged over the past 40 years, the mobile phone didn’t just get smaller, sleeker and easier to use, it also became a platform for other technologies. Mobile phones aren’t really phones anymore -- they’re computers that can make phone calls. The coalescence of technology has rendered the exact designation of a given device irrelevant. Tablet, phone, PDA, Google Glass – it doesn’t matter what a device is called -- today, mobile devices can do almost anything.

Mobile Phones of the Future

As mobile devices become smaller over the next 10 years, it’s likely that more devices will be built into clothing and accessories, following the lead of a wearable computer like Google Glass, said Scott Klososky, co-founder of consulting firm Future Point of View.

Smartphone 'Accessories'

The accessibility offered by application programming interfaces (APIs) for Android and Apple devices has led to millions of mobile apps.

For those who simply don’t trust the Weather Channel, for example, a small dongle called Thermodo (pictured above, and expected to be available in September 2013) will allow people to use their phones as an electrical thermometer.

A blood pressure monitor developed by Withings uses the iPhone as an interface for mobile health monitoring and tracking, while a series of mobile phone cases developed by Japanese manufacturer NTT DoCoMo allows users to measure radiation, ultraviolet radiation and body fat percentage.

Image courtesy of Thermodo/Kickstarter.com

“The device is becoming more and more like an outboard brain,” he said, adding that as more devices become connected in the Internet of Things, a mobile or wearable device will become a central hub for all the different sensors and devices in a person’s life.

Eventually, Klososky said, the mobile device will go from something people wear to something that’s implanted. “Now you can control your device just by thinking,” he said. “Ultimately I think that’s where we have to get to, because that’s the fastest form of controlling the device.”

Then, once everyone is outfitted with an implanted device controlled by their own thoughts, people will be able to connect to one another -- and to the Internet -- just by thinking, he said. With a heads-up retinal display and thought-powered computing, people would practically be telepathic.

“I’ve been reading science fiction since I was a kid, and when you really study what’s going on with technology and what’s out there today, what [the Defense Advanced Research Projects Agency] is developing – there are at least 1,200 people that have prosthetic arms that are connected to brain-computer interfaces," he said, adding that at least three companies have brain-computer interfaces that allow users to control behavior on a screen with their thoughts.

"The pieces are there,” he said. “When I think of science fiction now, I think of Star Trek.” Being able to “beam” to other places and enter warp drive is still science fiction, he said, but brain-computer telepathy is just common sense.

Happy birthday to the mobile phone, and here's to another 40 years of innovation and ingenuity.

Colin Wood Colin Wood  |  Staff Writer

Colin has been writing for Government Technology since 2010. He lives in Seattle with his wife and their dog. He can be reached at cwood@govtech.com and on Google+.