Free Thunderbird by Jack McDevitt Page A

reproduction a bit dicey.
    â€œWhich reminds me of another story about two birds and a bee that are out in the jungle when—Well, maybe we better let that one go.”
    Brad watched him for a moment, trying to decide whether to encourage him to continue, or move on. Finally: “Michael, do they breathe? Can you imagine an advanced life-form that doesn’t need lungs or gills?”
    â€œI’m glad to get an easy question. All the land animals we’ve seen so far on Eden seem to be breathing. We haven’t really had much of a look at the sea creatures. Microscopic life-forms can get oxygen directly, but larger forms need a way to absorb it into the body. If the organism is small enough, it can use spiracles, as some insects do. If its metabolism is slow enough, and its active tissue is spread out into the air, like the trees in the park across the street, then it can get by with stoma in the leaves. Once you get a larger organism, particularly a metabolically active one, you always need a way to pull in oxygen, transport it, and get rid of the carbon dioxide. Eventually, we may see an exception to this rule, but I couldn’t tell you what it might look like.”
    Another regular caller was on the line. Mark Collins, a retired guy with whom Brad occasionally ate lunch. “I guess people are interested in lungs and gills and stuff like that, but what we really care about is intelligence, Michael. Have you seen anything that’s intelligent?”
    â€œAgain, it’s early in the game. We haven’t seen anything we could talk to.”
    â€œSo who built the dome? Who was riding in the boat that was buried?”
    â€œWe have no idea, Mark. We’re going to have to be patient. Whoever built the Cupola is apparently not using it anymore. They may not have used it for thousands of years.”
    â€œBut it has power, doesn’t it?” said Mark.
    â€œSo does the Roundhouse. And that was dug out of the ground. Obviously, there are intelligent aliens in the mix somewhere, but we have no details. Except that it’s obvious they’re much more advanced than we are.”
    The show continued through two hours. Eventually, the question came that Brad knew was inevitable. “Professor Fossel,” the caller said, “we were always led to believe alien life, if it existed, would be radicallydifferent from what we see around us. Yet they look very much like the birds and cats and turtles that inhabit our own world. Some people say this demonstrates a purposeful Creator. Without getting into a religious discussion, what do you think?”
    â€œMy specialty is neurology, Caller, not theology. In my opinion we’ve seen nothing that either implies or rules out a purposeful Creator. From our standpoint, you can take your pick. I have to say, however, we are not surprised by seeing life on Eden resemble what we have here on Earth. But an obvious explanation for that is that Eden resembles Earth. Gravity, atmospheric makeup, water, temperatures. They’re all similar. There are only so many ways to make an organism fly or swim, so many ways to build an eye or an ear, to build a skeleton or a musculature. Turtles are a good example. If an organism needs protection, then the shape of the shell won’t vary much. It’s pretty much defined by the fact that an organism has a head and four limbs. Actually, those are good examples of common forms. Most animals will have a head that shares most of the common features found on Earth: a brain, some sensory inputs, and a mouth. They’re necessary to survive.
    â€œThe universe imposes certain constraints. It may not share a universal seed of life or a universal Creator, but it shares rules of physics. And that seems to be enough to get the job done.”
    The next caller wanted to know whether we were concerned about bringing back a plague?
    â€œIt’s highly unlikely,” Michael said. “A microbe that