Found this from
http://www.otherworlds.cx/supplements/aging.shtml
(From the d20 System Reference Document and the Dungeons and Dragons Player's Handbook)
The Open d20 system operates under the assumption that all characters start their adventuring career at the age of maturity or shortly after. Early adulthood is set as the baseline for character development, roughly equal to our high school graduation, or the age of eighteen in humans.
Of course, this does not remove the opportunity for some gamemasters to allow a player to run a pre-adult character. Realistically speaking, a bonus of two to all attributes would probably be evident from the age of thirteen to eighteen in all humans. But, don't use this as an opportunity to sneak in a fourteen-year-old rogue with 4d6 ability score rolls and expect your DM to give you twelve ability points when you turn eighteen. Pubescent development is difficult to run, when taking under consideration the physical and mental changes that occur. That translates to lower money, skill points, feats, and ability scores for your starting pubescent character in the game. The creators found this easier to eliminate from the system than develop a whole series of number crunching rules to further produce headaches for your gamemaster, and we thank them for it.
Upon growing into adulthood, and the logical starting point for your epic adventures, characters have reached a plateau, with abilities remaining unchanged from maturity through middle age. This can be rational, and is a bit generous to the characters. This assumes a certain level of physical exercise and a lack of destructive physical or mental afflictions. This is the prime of any character's life.
Upon reaching what is classified as middle age, age thirty-five in humans, the body starts to show signs of wear. Physical attributes drop slightly, one point each, and in return for three and a half decades of knowledge, assumedly put to good use, mental abilities benefit the same increase of one point. Life has brought with it knowledge, a better grasp on life, and a better grasp of self. Affects are negligible for the most part, effecting characters only slightly. It can be argued that a tough workout regimen could keep physical attributes at their same level, while gaining one point each in the other attributes. But, after years of adventuring, joints stiffen, ligaments and tendons develop scarring, and due to changes in physiology, the body becomes less able to repair itself when damaged, and becomes more fatigued when taxed. But, of course and as always, this is at the discretion of the gamemaster.
There is no turning point once old age is reached, fifty-three in humans. The body is tired and there is no stopping physical degradation. Physical attribute loss is two each to strength, constitution, and dexterity. Wisdom, Intelligence, and Charisma again increase by one. In spite of loss of physical prowess, the character is distinctly aware of his capabilities and how to apply his experiences to life situations. Again it could be argued that an extremely regimented workout could maintain physical attributes, but note that this occurs today with less than one percent of the world population. Calcium is leached from the bones, those once soft joints have hardened, losing mobility and dexterity, and the body in no way can repair damage as quickly as it did twenty years previous.
Venerable age signifies the extreme of human life. For humans, this is approximately seventy years of age. This is the point in life where all the physical punishment delivered to the body comes back with a vengeance. Physical attribute loss is three for strength, constitution, and dexterity. Again, the years reward wisdom, intelligence, and charisma with a bonus of one. No level of nonmagical assistance will ever get back those bulging biceps, powerful pectorals, or that shapely or lithe figure.
So, in a nutshell, a human with straight twelve abilities at thirty years old would by venerable age have a strength, dexterity, and constitution of six, and a wisdom, intelligence, and charisma of fifteen. This might be why we run across those gnarly decrepit wizards that can't hold up their arms, but can throw off those ninth level spells like cantrips; and the fighters, those poor fighters, take desk jobs.
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