RimWorld Age Secrets: Biological vs Chronological Demystified

Why two ages?

In the sci-fi universe of RimWorld, space travel and cryptosleep can halt aging. A pawn might be biologically 22 but chronologically 200 because they spent most of two centuries asleep in a casket. This explains bizarre family pairings (like an 83-year-old mother whose father is 16 biologically – he was in stasis while time passed). Chronological age adds story flavor and helps make sense of such scenarios. New to RimWorld? Start with our complete beginner's guide.

Example of how biological and chronological ages are displayed in RimWorld

Age Limits

Humans never die strictly of old age; there's no hard age limit. However, as pawns grow biologically older, they accumulate age-related health problems which can ultimately be fatal. RimWorld humans have a nominal life expectancy (~80), after which health issues become more frequent.

Age-Related Ailments

Once a pawn passes middle age (around 40), there's a chance each year on their birthday they develop chronic conditions. Common ailments are:

• Cataracts (eyesight loss)
• Hearing loss
• Bad back
• Frailty
• Dementia (in extreme old age)

For comprehensive treatment strategies, check our complete medical guide.

Work and Skills

There is no built-in skill bonus or penalty just for being older. A 70-year-old and a 20-year-old with the same stats perform equally unless the older has health issues. In practice, older pawns often spawn with higher skills due to backstory.

Ideology - Age Reversal

The Ideology expansion added a biosculpter pod that lets colonists undergo an Age Reversal cycle. This feature was mainly for transhumanist ideologies whose followers wanted to stay young. The pod could rejuvenate a pawn by 1 year biologically per cycle.

Gameplay Tip

Even without Biotech, you can use Ideology's age reversal to maintain a colony of youthful, healthy pawns. Many players with transhumanist colonies set up a rotation of biosculpter pods so no one ever exceeds biological mid-age, avoiding frailty and other conditions.

Life Stages

Accelerated Childhood

To make raising children viable within a normal playthrough, RimWorld Biotech uses accelerated aging for youth by default:

• Child Aging Rate: 400%. Up to age 11, kids age 4 years biologically for every 1 year chronologically.
• Tween to Adult Smoothing: From 11 to 18, the aging rate linearly slows down from 4× to 1×.
• Overall: It takes ~415 in-game days (6.9 years) for a newborn to reach biological 20.

These rates are configurable in the Storyteller settings.

Growth Moments

At certain ages (biologically 7, 10, and 13), child pawns have growth moments where they graduate in abilities and you can choose traits or passions for them.

Child Work and Limits

• Kids have reduced stats due to their body size and youth.
• Certain work types remain off-limits until a growth moment unlocks them.
• Children can fight but may have the "Fleeing Fire" mental response.
• Until 13, children are considered "noncombatant" by enemies.

Key Insight

All told, Biotech introduced a whole life cycle for colonists. Chronological age simply tracks how long it's been since birth, but biological age determines what the pawn can do at the moment. A child frozen in cryptosleep won't grow up – their biological clock stops while inside.

Biotech expansion's life stages from babies to adults with growth mechanics

• A growth vat ages a pawn at 20× normal speed (2000% the normal rate) as long as it's powered and fed with nutrient solution.
• In game terms, you can grow a newborn into an 18-year-old adult in ~63 days using vats (about 2 months).
• Comparatively, natural/accelerated raising would take ~198+323 days to reach 18. So vats are roughly 5–6× faster than the already accelerated default childhood.

Other Gene Effects

• Long Lifespan Genes: Some xenotypes (custom races) can have different natural lifespans, slowing the onset of age ailments.
• Fertility Genes: Biotech adds genes that modify fertility (e.g., Fertile or Sterile) which can counteract age-related fertility decline.
• Aging Speed Genes: Some xenotypes effectively age faster or slower as a racial trait.

Overall Impact

Gene-modding means you can custom-tailor how aging affects certain pawns. You could create an immortal colonist by implanting Ageless (if you get an Archite capsule and the gene). They would biologically stay 18, effectively eliminating all age-related issues.

Gene modification system with Ageless and other aging-related genes in Biotech

Fertility by Age

Human fertility in RimWorld follows a curve – it peaks in early adulthood and drops as a pawn ages:

• Fertility starts decreasing after ~age 25 and is near zero by around 50.
• The game assigns each pawn a fertility percentage; young adults are 100%, and it diminishes with age.
• This mirrors human biology where women have menopause and men also become less fertile with age.

Pregnancy and Age

• Only women colonists between ages ~16 and ~50 can get pregnant (naturally).
• Past a certain age, pregnancy may be riskier or just unlikely.
• Without mods or genes, it's hard to get a pawn over 45 pregnant because their fertility stat has dropped significantly.

Effects of Chronological Age

Chronological age does not impact fertility at all – a pawn who is biologically 30 and chronologically 1,030 (slept a millennium) will behave as a 30-year-old in fertility. Conversely, a pawn who is biologically 60 but chronologically 20 is effectively post-fertile; the body's age is what matters.

Related Tech/Genes:

• The Ageless gene indirectly guarantees a pawn never becomes infertile due to age.
• The Age Reversal effect from biosculpters can restore fertility as well.
• Biotech also introduced assistive reproduction (IVF, embryo implantation). Even an older pawn could serve as a surrogate or provide an egg.

Note on Sanguophages (Vampires)

These pawns are Ageless – they do not age or lose fertility. A 200-year-old vampire can still impregnate or get pregnant as if they were 18. This makes them valuable for breeding if you want to maintain a bloodline. Learn about recruiting special pawns like sanguophages.

Work Capabilities by Age

Combat and Age

Younger adult pawns have a slight edge in that they likely have no movement or sight impairments. An 80-year-old with cataracts and bad back is a poor shooter and slow to reposition. Replacing aged body parts with bionics can fully restore combat performance, though. For detailed combat strategies, see our comprehensive combat and defense guide.

Healing and Immunity

Older characters have weaker immunity gain speed against diseases. Very old pawns are less likely to survive infections because their immunity grows slower. Installing a youth serum (if modded) or using age reversal can indirectly improve a pawn's disease resilience. Age also affects movement speed - learn about optimizing pawn movement and pathfinding.

Countering Age Effects

To maintain performance of older colonists, players often use: bionic parts (spine to fix bad back, bionic eyes for cataracts, etc.), healer mech serums, or biosculpter pod healing cycles. With Biotech, giving an older pawn a gene like Ageless in mid-life will stop any further decay.

Other Methods

• Healer Mechanites & Serums: While not directly reducing age, items like the Healer Mech Serum can cure one random chronic condition. This means an older pawn can be functionally rejuvenated by periodically curing their worst ailment.
• Age Reversal Serum (Mod): Some mods add a craftable or rare item that directly reduces a pawn's biological age by a certain number of years.
• Artificial Youth (Mods): Mods such as Polarisbloc introduce surgeries for age manipulation.

Gameplay Note

Between these tools, dedicated players can keep their favorite colonists around indefinitely. Stories of colonies with 150-year-old founders who are still biologically 25 (thanks to countless biosculpter cycles) are not uncommon. Just remember to manage the mood impacts – transhumanist pawns want age reversal regularly, while others might be disturbed by it.

1. Embrace Cryptosleep for Travel or Emergency

If you have colonists who are getting very old and frail, you can put them into a cryptosleep casket to halt their aging until you have a solution (like a serum or sufficient Luciferium drug). This is essentially "suspending" a pawn's problems.

2. Use Age to Your Advantage in Story

Don't ignore chronological age for storytelling! For example, a colonist who is "24 (312)" might have knowledge of past events or carry psychological trauma from a long life. Some players role-play that very high chronological age pawns have wisdom or old-world knowledge.

3. Enhance and Replace Aging Body Parts

For older pawns, bionics are your friend. Replacing eyes, ears, spine, legs, etc., will nullify most age penalties. An 80-year-old with a bionic spine (to fix bad back) and bionic eyes (for cataracts) is effectively as capable as a young adult – even more so with advanced bionics. Learn about optimizing colonist equipment and gear.

4. Transhumanist Ideology Buffs

If you play with an Ideoligion that venerates youth or rejects aging, leverage those precepts. A Transhumanist colony expects regular age reversal – fulfilling this keeps a mood buff ("Age reversal demanded satisfied"). For more mood management tips, check our room impressiveness guide.

5. Child Rearing Tips

• Safety First: A common trick is to run a single tile of power conduit in a wide perimeter around your base – children treat conduits as "structures" and won't wander beyond the furthest conduit. For more base design tips, see our optimal colony layout guide.
• Education: Build a school area with blackboards and desks. A blackboard in a room gives a bonus to learning for children present.
• Growth Vat Utilization: Use vats strategically. Many players vat-grow babies to children, then raise them, then maybe vat the last bit of teenage years.
• Don't Forget Teens Can Work: Once a kid hits 13, they are basically an adult workforce with slightly lower efficiency. Don't leave them on playtime all day.

6. Using Aging to Control Wealth

Child pawns have lower market value than adults of equivalent skill (because of their work limitations). This means a colony with several children might have lower raid strength than the same colony with those children aged up – effectively letting you train future fighters without immediately increasing difficulty.

Biotech Release (Oct 21, 2022)

Introduced babies, children, and chronological vs biological age tracking for human pawns. Chronological age added to UI (in parentheses) for humanlikes. Age-related mechanics like fertility and child growth implemented. Sanguophages (immortal vampires) added with Ageless genes.

Nov 7, 2022 – Update 1.4.3555

Tweaks to child aging. "As people grow up, their aging rate now smooth scales from child rate to adult rate over several years. This prevents... having a lot of 13-year-olds after raising children." Also added a stat readout for current age rate multiplier on pawns.

Nov 29, 2022 – Update 1.4.3562

Children immediately update to adult body/backstory at 18 instead of waiting for a tick. This prevented awkward cases where a pawn stayed "child" a bit after turning 18.

Dec 2022 – Update 1.4.3580

Ideology integration: Added a positive thought for parents whose child is not in a growth vat if their belief prohibits vat use (and vice versa). Age reversal tweaks: Reduced biosculpter cycle time.

Jan 19, 2023 – Update 1.4.3613

Bugfixes: "Fix: Baby to child dialog becoming locked." Resolved some edge cases with learning need freezing.

May 2024 – Update 1.5.4104

Minor fix: "Fix: Inhumanized not nullifying childbirth related memories." Also fixed a rare bug with age reversal.