There are a few truths in the automotive world that have always been held to be completely self-evident. Wheels are round. British cars are unreliable. Audis understeer. And dammit, a real Porsche must be shaped like a bathtub and, like that bathroom fixture, must have all of its mechanicals hanging out at one end - the rear. There have been attempts to buck the trend along the way, but even if cars like the 944 were sales successes, the most diehard of Porsche loyalists never clasped them to their breasts. Even the current Boxster, a perfectly balanced, gold medal-caliber track athlete, has failed to gain acceptance in many Porsche circles, simply because of its toplessness. Enter the Cayman: a stiffer, more aggressive Boxster with a welded-on-with-testosterone roof. It isn't exactly a bathtub - more a Jacuzzi, with shallow ridges around the end and a deeper section in the middle - and the engine isn't quite at the rear, but it is at least close. Is this entry-level Stuttgart sportster worthy of the Porsche crest? We'll put it side-by-side with the Porsche family patriarch - a 911 Turbo - to search out the common DNA.

Sitting in the driver's seat, the similarities between the $49,400 Cayman and the $122,900 Turbo are surprising. The seating position, the seats themselves, and the gauge clusters have a common bond, as if to say, "Zis is how zee Porsche feels, regardless of zee price." It is the same vibe that 911s have had for decades, with a simple, minimalist dash (key to the left of the steering wheel, tach in the center of the gauge cluster), a high seating position, and a low greenhouse for impressive visibility in all directions. The biggest difference, other than the 911's back seat, is the quality of materials. The Turbo's seats, steering wheel, and dashboard are all slathered in high-grade leather, while the headliner is soft Alcantara. The Cayman sneaks a little more plastic in, although for the right price, Porsche will cover almost anything - including the air vents - with leather. Both use carpet on the bottom half of the door panels, an odd detail that was common in the '70s, but is unique to Porsche in 2007. Outdated, sure, but these kitschy details give Porsche a change-for-performance-or-necessity-only sort of ethos. It's also what gives the Cayman an evolved-through-generations feel, despite the fact that it has only existed for two years. Even the Cayenne SUV has a bit of the familiar layout, the heritage feel that is common among Porsches.

What the Cayenne doesn't have, though, are the coarse rumblings of a flat 6 creeping around the back of the driver's ear. As a whole different breed of automobile, Porsche's sport-ute gets away with it, whereas the 928 and 944 didn't. The Cayman actually amplifies the experience of the 911; those special sounds sit in the back seat, rather than behind it, making a mash of the throttle all the more aurally entertaining.

It isn't in Porsche's nature to favor bark over bite, and the Cayman is indeed as much a track star as its forced-induction father. Without the weight of an engine over the front wheels, both cars boast a steering feel that is light, quick, and unadulterated. As the front wheels negotiate an apex, the wheel provides a kickback-free experience, wiggling gently as the driver makes small, quick corrections to maintain course. It's one of the more important things that keep these two Porsches special in a world turning more and more toward artificial-feeling electric steering. Suspension compromises - or a lack thereof - are a commonality between the cars as well. These are purpose-built machines, and while the Turbo is sprung slightly more stiffly, neither car is meant for the wife's Saturday run to Whole Foods. Yet at the same time, these Porsches are easy and enjoyable to drive on the street, since everything works in mechanical harmony. The Turbo's optional Tiptronic shifts itself nearly as quickly and appropriately as most can manage with the Cayman's standard 5-speed manual box. But while both cars have an inherent Porsche-ness to their driving manners, they do have some differences.

The 245-horsepower Cayman doesn't get its quickness from pure power, but through perfect balance. With the engine mounted amidships, the Cayman is predictable and confidence inspiring on the track (our local Gingerman Raceway, in this case). The driver can keep his foot down because the car doesn't plow, it doesn't step out; it just goes. Work hard to upset the chassis, and the car will slide - albeit in a smooth, controllable drift. It is a car that's easy to master, yet incredibly fun to flog all day long once you do. The Turbo takes a whole day just to learn.

Other than its nearly double the Cayman's horsepower, the 911 Turbo' s biggest advantage here is its brakes. Lots and lots of brakes. Not that the Cayman's brakes fade, but the Turbo's optional, $8840 carbon-ceramic brakes actually unfade - the more you stomp on the pedal, the more it pushes right back at you. Other race-inspired goodies like sodium-filled exhaust valves, a dry-sump oil system, variable-geometry turbochargers, and aluminum doors also help justify the Turbo's top-shelf price, and its exclusivity is bolstered by its track manners. If the Cayman is Porsche's beginner's car, a 911 Carrera would be the intermediate, and the Turbo is an experts-only ordeal. The brakes are so strong, standing on them sends the car into an unnerving, deep-in-the-corner dance as the rest of the car struggles to keep up with the stopping power.

The Turbo's straightaway speed is its other advantage over the Cayman. Porsche claims that the 911 Turbo will run a sprint from 0-124 mph (200 km/h) in just 12.2 seconds, as compared to the Cayman's 23.7-second time. But managing that power can be tricky, and takes some practice. In my experience, better lap times can actually be achieved with the car's stability control left on, as lift-throttle oversteer will bite your hindquarters like an angry guard dog. Sure, you start getting used to it and can begin to anticipate the car's moves, but the smallest error can lose you a second or two. After a full day at the track, the Cayman leaves you with a sense of satisfaction and conquest. As the Turbo drives off into sunset, I feel like I've been sucker punched and now the guy's leaving the bar with my girl. All I want is one more chance to show up the Porsche's dynamics, one more opportunity to knock a few more tenths off my lap time.

For all the divergent feelings the two cars engender, their Porsche-ness is never in question. Both are, as you'd expect, very quick. Despite the Turbo's power and braking advantages, the lighter, more balanced Cayman makes its way around Gingerman's 1.9-mile course with surprising quickness. The Turbo managed to clock a lap time of 1:37.8, while the base Cayman was close behind at 1:39.5. That means that on our test track, less than two seconds separate Porsche's range of coupes (GT3s excepted, natch).

The Cayman isn't a 911, but it is definitely a Porsche, in much the same way that, despite decades of fighting it, we're all a bit like our parents. It has similar but more youthful looks both inside and out, and the Cayman's sounds and feel are 911-like, too, but harder-edged and nimbler. It's not easy when your father is the Keith Richards of sports cars, though, rocking the world and thrusting his hips since the mid-'60s. The Cayman handles that pressure well, and doesn't go for mimicry. It's more down-to-earth, more refined and better mannered. But get it out on a track and, well, you know what they say . . . like father, like son.