New estimates indicate that males are not larger than females in most mammal species

Sexual size dimorphism has motivated a large body of research on mammalian mating strategies and sexual selection. Despite some contrary evidence, the narrative that larger males are the norm in mammals – upheld since Darwin’s Descent of Man – still dominates today, supported by meta-analyses that use coarse measures of dimorphism and taxonomically biased sampling. With newly available datasets and primary sources reporting sex-segregated means and variances in adult body mass, we estimated statistically determined rates of sexual size dimorphism in mammals, sampling taxa by their species richness at the family level. Our analyses of wild, non-provisioned populations representing >400 species indicate that although males tend to be larger than females when dimorphism occurs, males are not larger in most mammal species, suggesting a need to revisit other assumptions in sexual selection research., These data on sex-segregated body mass means and variances were collected from the literature, including existing published datasets and from primary sources. We sampled mammalian families according to their species richness (including the orders and families comprising at least 10 species). We excluded data from sexually immature, captive-bred or food-provisioned, or pregnant individuals when these data were distinguished or when it was indicated that they were mixed into the data (see Methods section in manuscript for the few exceptions). Estimates from museum specimens were generally not used as we wished to make within-population comparisons between the sexes, and domesticated species were excluded apart from semi-domesticated free-ranging reindeer (Rangifer tarandus). Whenever sex-segregated means and variances for body length were presented alongside body mass data in a study included in the dataset, these data were also harvested. Prior to analyses, we filtered the full dataset (..., , # New estimates indicate that males are not larger than females in most mammal species

These files include the R code and raw data used for all analyses and data visualizations in the associated manuscript:

Tombak KJ, Hex SBSW, Rubenstein DI. 2024. New estimates indicate that males are not larger than females in most mammal species. Nature Communications.

## Description of the data and file structure

FILE LIST:

SSD_Paper_Code.R: R code used for analyses and generating figures in the manuscript and supplementary materials.

Tombak_etal_SSDinMammals_FullDataSet.csv: the full set of raw data used for analyses and data visualizations.

Tombak_etal_SSDinMammals_FullDataSet.ods: the same as above, in ods format.

Num_Spp_perFamily.csv: data on the number of species per family in each mammalian order with at least ten species, as well as the families of the order Pilosa sampled in our study. These data are from Burgin et al. 2018 (full citation below).

Num_Spp_perFamily.ods: the same a...

性体型二态性（sexual size dimorphism）催生了大量关于哺乳动物交配策略与性选择的研究。尽管存在部分相悖证据，但自达尔文《人类的由来》以来便被确立的“雄性体型更大是哺乳动物常态”的叙事，至今仍占据主导地位，这类结论得到了采用粗糙二态性度量与分类学偏差采样的荟萃分析的支持。借助新公开的数据集与报告了成年体重按性别划分的均值与方差的原始文献，我们以科阶元的物种丰富度为采样依据，对哺乳动物的性体型二态性统计发生率进行了估算。我们对涵盖400余种野生、未被人工补给的种群的分析显示，即便在发生性体型二态性的类群中雄性往往体型更大，但多数哺乳动物物种的雄性体型并不大于雌性，这表明有必要重新审视性选择研究中的其他假设。

本数据集的按性别划分的体重均值与方差数据均来自文献，包括已公开的已发表数据集与原始一手文献。我们依据物种丰富度对哺乳动物科进行采样（涵盖物种数≥10的目与科）。若数据可区分或被标注为混杂了未性成熟、圈养繁育、人工投喂或怀孕个体的信息，我们将此类数据予以排除（极少数例外情况详见论文方法部分）。由于我们旨在开展种群内的两性比较，因此一般不使用馆藏标本的估算数据；同时除半驯化的自由放养驯鹿（*Rangifer tarandus*）外，所有驯化物种均被排除。若纳入本数据集的研究同时提供了按性别划分的体长均值与方差数据，我们也将此类数据一并收录。在开展分析前，我们对完整数据集进行了筛选（……）# 新估算结果显示：多数哺乳动物物种的雄性体型并不大于雌性

本套件包含用于关联论文中所有分析与数据可视化的R代码与原始数据：
Tombak KJ、Hex SBSW、Rubenstein DI，2024年。《新估算结果显示：多数哺乳动物物种的雄性体型并不大于雌性》，《自然-通讯》（*Nature Communications*）

## 数据与文件结构说明
文件清单：
1. SSD_Paper_Code.R：用于论文及补充材料中的分析与图表生成的R代码
2. Tombak_etal_SSDinMammals_FullDataSet.csv：用于分析与数据可视化的完整原始数据集（CSV格式）
3. Tombak_etal_SSDinMammals_FullDataSet.ods：与上述数据集完全一致的ODS格式文件
4. Num_Spp_perFamily.csv：各物种类群（含物种数≥10的目）的科阶元物种数量数据，以及本研究采样的披毛目（Pilosa）各科的相关数据，此类数据源自Burgin等人2018年的研究（完整引用见下文）
5. Num_Spp_perFamily.ods：与上述内容一致的ODS格式文件