(CNET) -- Consider the blind mole rat. The evolutionary process has given these subterranean rodents, classified as the genus Spalax, massive teeth and tough claws for digging -- and more or less zero eyesight.
But blind mole rats still have eyes. They're just very, very small and so obsolete that they're now completely covered by a layer of skin.
This is what's taught in biology classes as a "vestigial feature," along with other zoological examples, such as the human appendix, snakes' pelvic structures, emus' wings, and whales' hind leg bones.
Now, take a different kind of evolution: the constantly changing, expeditious array of products and features that make up Facebook.
In the past few months, the updates and revisions have been coming even faster than usual. The latest, announced yesterday, included a big revamp for Facebook's longstanding "groups" feature.
What used to be potentially massive interest groups are now pitched as small, intimate ways to connect with friends, family, and fantasy football league members.
But the "old groups" aren't gone -- you just can't create them anymore -- nor are the "friend list" groupings that Facebook hopes the new groups will ultimately parallel in purpose. They're still around. They're more or less Facebook's own vestigial limbs.
Facebook is going to keep evolving. And it's likely going to run into more instances where it chooses to keep alive an otherwise obsolete feature that has just enough users that killing it would be problematic. What will this mean for Facebook's overall code and product experience, if it's peppered with the equivalent of, say, emu wings?
It's not an easy question to answer. Developers, for one, aren't in agreement.
"Well, look at Facebook already. It's a massive piece of s**t," said Kyle Bragger, the proudly irreverent founder of developer and designer community site Forrst. "It's super bloated because it's the 'kitchen sink' -- and now, on top of that, they're forking features. It's like the same feature set in two implementations to support two groups of users: users who are p***ed the feature is changing, and users who don't care."
Bragger said operating separate features for the same function is sloppy and will invariably lead to problems down the road.
In this case, it's complicated: Facebook was dissatisfied with its "friend list" feature, which allowed members to selectively direct status messages and privacy settings toward groups of contacts from their friends lists.
According to CEO Mark Zuckerberg, only about 5 percent of members used it. Still, that's more than 25 million. And it's safe to say that Facebook would have a privacy scandal of apocalyptic proportions if it chose to do away with the intricate settings that those millions of people have put in place, potentially exposing very personal information that some had shielded from less intimate contacts on their friends lists.
To that, Bragger said, "Well, Facebook already sucks at privacy."
But not all those in the developer community believe that these "vestigial limbs," in this case the "old groups" and friend lists, could pose a problem with regard to efficiency or user experience.
"For me, this is a sign that they have made the commitment to be a platform, not just for code but for people; as Zuck said, 25 million users is enough that you don't want to cut them off," said Kevin Marks, a Google and Apple veteran who now works at BT as vice president of Web services and blogs at Epeus' Epigone.
Marks said Facebook's choice to maintain the "old groups" and friends lists is connected to the fact that it recognizes that not all members use it for the same thing. One Facebook user's vestigial limb can be another's core experience.
"When I was working on QuickTime at Apple around 2000, we wanted to make sure to never leave a QuickTime movie behind -- each new version had to play all the old movies, whether we had come up with a better way to do things since or not, and that old version shouldn't crash when given a movie made by a new version," Marks said.
"With the Web, this is less of an issue, as you can upgrade the whole code base for everyone at once, but over time, you do gather a diverse set of users who have found their own uses for your features."
Another developer who spoke to CNET also brought up the fact that it's not entirely clear as to how many of Facebook's features this kind of situation is applicable. He pointed out Facebook's recent revamp of Facebook Photos, which introduced a new interface last week, and the fact that no "old" features were left behind.
The counterargument there is that with Photos, Facebook didn't have to do away with any existing features in the name of a change in product direction, nor would maintaining an old feature prevent some kind of privacy scandal.
It won't happen with every Facebook product launch, but given how many of them there have been lately, it could very well happen again, and the vestigial or "forked" features could start to build up.
What it comes down to, Marks said, isn't the mere existence or nonexistence of vestigial features, but rather how Facebook handles them. "Done right, the old stuff becomes the substrate for the new, and different groups can emerge," he said.
But he did have one early criticism: "I do think Facebook should have given this new feature a different name, [because] if you have any old-style groups, it is very confusing indeed."
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