On Oct. 29, 1969, UCLA student Charles Kline sent the first message over the ARPANET, the computer network that later became known as the Internet. Though only the "l" and "o" of his message ("login") were successfully transmitted, the interactive exchange ushered in a technological revolution that has — as anyone alive long enough to witness the shift knows — revolutionized human interaction.

"This ARPANET experiment that we're essentially celebrating right now, while it's not the Internet it is certainly one of the foundations of the Internet," said Vinton Cerf, vice president and Chief Internet Evangelist at Google. Cerf, along with Robert Kahn, Chairman, CEO and President of the Corporation for National Research Initiatives (CNRI), are considered the fathers of the Internet as they created the so-called TCP/IP protocol that allowed various independent networks to link up to form a network of networks, or the Internet.

That was 40 years ago Thursday, and since then, the ability to communicate with others, share information and just be connected has drawn more than a billion people online. And so the ARPANET, and later the Internet, was both supported by and fostered innate human nature — the need to be social and share information.

"Don't let anyone tell you that information is power," Cerf told LiveScience in a telephone interview today. "It's information-sharing that's power."

The results can be seen in all walks of life, from how we treat an illness (search engines have become our virtual doctors) and find travel information (real, live travel agents are so yesterday) to hooking up with old friends and family, for better or worse.

"A few decades ago, no one imagined the transformation that loomed ahead. The experts didn't even see it coming," said Cathy Davidson, a researcher of digital interactive learning at Duke University. "Checking our Facebook page before making the morning coffee? Googling our symptoms to decide whether or not to call a doctor? Any 20th-century expert viewing this future in a crystal ball would have declared it pure science fiction."

And the evolution of the Internet is a Petri dish for human adaptation.

"The explosion of the usage was certainly a surprise, that people were adapting to it so quickly," said Hans-Werner Braun of the University of California, San Diego. Braun was an integral part of the creation of NSFNet, which was to be a network of networks and which connected academic users along with the ARPANET, beginning in 1986.

Get connected

On the Internet, some ideas about rational choice, such as the theory that people make decisions based on profit, get tossed out the window.

"The Internet wasn't created that way," Davidson said. Rather, it was set up as "an open source structure not about profit." She added that the purpose of the Internet was to allow the entire world to interact.

The value of an interaction or a stint online can now be measured by our ability to share.

"What really surprised me more than anything was the response to the World Wide Web, which was an avalanche of information that poured in from the users of the Internet," Cerf said. "People really wanted to share what they knew. They weren't necessarily doing this because they wanted material compensation. Many of them were sharing information simply for the satisfaction of knowing that it was useful for somebody else."

Such sharing requires give-and-take.

"We are learning not so much how to receive information as we did from other forms of media, the way we would watch TV or read a novel. We're now involved in online communities where we are contributing to the Internet exchanges," Davidson said, adding it's an iterative process.

The idea of what makes an expert has also been called into question. "In the past, we might assume that the best information we could get from a source is from an expert," Davidson said. "If I'm about to take a trip, now I can go to Fodor's, written by experts, or I can go to tripadvisor.com where people like you and me give you tips. That's a fascinating shift in human ideas of what constitutes knowledge and expertise."

Network central

In our day-to-day lives, the Internet has allowed us to do more, some say.

"Now we live our lives in multiple networks that aren't very well-connected, and we juggle between these networks," said Barry Wellman, director of NetLab at the University of Toronto in Canada. "The Internet helps that because it allows us to maintain multiple relationships."

In this scenario, Wellman would say we are each at the center of various networks and we easily maneuver between these. For example, one could imagine speaking with a colleague on Skype, answering e-mails from various others in different networks and perhaps engaging with a family member or other in your office.

Part of this is the result of the Internet, including social networking sites, allowing us to reach out to a much greater volume of people just about anywhere.

As of this September, more than 50 percent of Internet users in the United States say they have a wireless connection via a laptop, cell phone, game console or other mobile device, according to the Pew Research Center. And nearly 20 percent of such Internet users share updates about themselves and read posts by others on Twitter and other similar services.

"We've moved away from a group-based society to a network-based society," said Wellman, adding this is a "major social transformation."

For instance, while in a group-based society (think a village), you might contact your next-door neighbor to help you out when sick, in a network-based society you'd be more likely to reach out to various people in various networks, including an e-mail group you've joined.

The good and the bad

Like Pandora's box, the Internet has its vices.

Cerf points to viruses and worms, identity theft and keystroke loggers. "There are bad things that happen on the Internet. Like any other infrastructure, it's possible to abuse it," Cerf said.

"On the other side, the positive benefits of having this infrastructure in place and the ability to allow people to share information and interact with each other, in my view, vastly outweigh the abusive side effects."

This seeming ubiquitous access to the Internet also means many of us are always wired.

"We certainly have the ability of continuous presence. We're expected to be available at all times, so much so that my students get mad at me when I don't respond to them at midnight on a Saturday night," Wellman said.

His research in the United States and Canada is showing people are embracing such all-pervasive connectedness. Rather than taking away from their lives, the Internet is adding to them, he has found.

The fact that such Internet connections are not face-to-face could have some negative consequences, according to Frans de Waal of Emory University and the Yerkes Primate Center, where he studies the evolution of human behaviors through primate research. Some of those consequences include the inability to interpret a facial expression, he said.

"In face to face contact primates try to avoid conflict, try to settle disputes either before or after they happened for the simple reason that disputes most of the time do not advance the interests of a social, cooperative species," de Waal said.

He also thinks humans rely on open conflict as a last resort. "On Internet blog and comment sites, however, one often gets the impression that people are out to get aroused and vent feelings that normally they would keep for themselves. The social consequences of such behavior have been removed."

Future networking

If you're wondering if the Internet is in your future, Cerf says, "resistance is futile."

"I would say again that the Internet would not have happened if the ARPANET experiment had not been so successful. The Internet's amazing adaptability over the last three decades has surprised many people, including me," Cerf said. "I don't see any end in sight."

And he has high expectations for the future reach of the Internet. "I would guess that we have on the order of 2 billion people online now. I would guess half the world's population will have some access between now and the end of 2011. By the end of the next decade I think between 75 and 85 percent of world's population will be online."

In fact, connections could go beyond Earth.

"I am confident we will see the Internet go off planet," Cerf said. He has been working with a team of engineers at NASA's Jet Propulsion Laboratory and other NASA agencies since 1998 on the so-called Interplanetary Network.

"We are in the last stages of space qualifying an interplanetary Internet protocol that could be used by both manned and robotic spacecraft to communicate with each other and the planet Earth," Cerf said.

Dave Brody contributed to this report.